rasterize: unexpected necessity: render any convex polygon without triangulating (more complex polygons can be created by culling)
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@ -26,6 +26,10 @@
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//the shape rasterizers contained herein are based on code supplied by Chris Hecker from
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//http://chrishecker.com/Miscellaneous_Technical_Articles
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//The worst case we've managed to think of so far would be a viewport zoomed in a little bit
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//on a diamond, with cut-out bits in all four corners
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#define MAX_CLIPPED_VERTS 8
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#include "rasterize.h"
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#include <algorithm>
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@ -166,11 +170,12 @@ struct Fragment
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u8 pad[5];
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};
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static VERT* verts[4];
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static VERT* verts[MAX_CLIPPED_VERTS];
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static VERT* sortedVerts[MAX_CLIPPED_VERTS];
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INLINE static void SubmitVertex(int vert_index, VERT* rawvert)
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INLINE static void SubmitVertex(int vert_index, VERT& rawvert)
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{
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verts[vert_index] = rawvert;
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verts[vert_index] = &rawvert;
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}
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static Fragment screen[256*192];
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@ -349,42 +354,6 @@ struct Shader
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} shader;
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struct Interpolator
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{
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float dx, dy;
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float Z, pZ;
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struct {
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float x,y,z;
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} point0;
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Interpolator(float x1, float x2, float x3, float y1, float y2, float y3, float z1, float z2, float z3)
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{
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float A = (z3 - z1) * (y2 - y1) - (z2 - z1) * (y3 - y1);
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float B = (x3 - x1) * (z2 - z1) - (x2 - x1) * (z3 - z1);
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float C = (x2 - x1) * (y3 - y1) - (x3 - x1) * (y2 - y1);
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dx = -(float)A / C;
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dy = -(float)B / C;
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point0.x = x1;
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point0.y = y1;
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point0.z = z1;
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}
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void init(int x, int y)
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{
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Z = point0.z + dx * (x-point0.x) + dy * (y-point0.y);
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}
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FORCEINLINE int cur() { return iround(Z); }
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FORCEINLINE void push() { pZ = Z; }
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FORCEINLINE void pop() { Z = pZ; }
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FORCEINLINE void incy() { Z += dy; }
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FORCEINLINE void incx() { Z += dx; }
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FORCEINLINE void incx(int count) { Z += dx*count; }
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};
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static void alphaBlend(Fragment::Color & dst, const Fragment::Color & src)
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{
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if(gfx3d.enableAlphaBlending)
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@ -628,8 +597,8 @@ inline long Ceil28_4( fixed28_4 Value ) {
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struct edge_fx_fl {
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edge_fx_fl() {}
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edge_fx_fl(VERT **pVertices, int Top, int Bottom );
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inline int Step( void );
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edge_fx_fl(int Top, int Bottom);
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inline int Step();
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long X, XStep, Numerator, Denominator; // DDA info for x
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long ErrorTerm;
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@ -659,8 +628,7 @@ struct edge_fx_fl {
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void doStepExtraInterpolants() { for(int i=0;i<NUM_INTERPOLANTS;i++) interpolants[i].doStepExtra(); }
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};
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edge_fx_fl::edge_fx_fl( VERT **verts, int Top, int Bottom )
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{
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edge_fx_fl::edge_fx_fl(int Top, int Bottom) {
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Y = Ceil28_4(verts[Top]->y);
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int YEnd = Ceil28_4(verts[Bottom]->y);
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Height = YEnd - Y;
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@ -690,7 +658,7 @@ edge_fx_fl::edge_fx_fl( VERT **verts, int Top, int Bottom )
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}
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}
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inline int edge_fx_fl::Step( void ) {
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inline int edge_fx_fl::Step() {
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X += XStep; Y++; Height--;
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doStepInterpolants();
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@ -703,8 +671,8 @@ inline int edge_fx_fl::Step( void ) {
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return Height;
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}
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void hecker_DrawScanLine(edge_fx_fl *pLeft, edge_fx_fl *pRight)
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//draws a single scanline
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static void drawscanline(edge_fx_fl *pLeft, edge_fx_fl *pRight)
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{
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int XStart = pLeft->X;
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int width = pRight->X - XStart;
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@ -747,60 +715,93 @@ void hecker_DrawScanLine(edge_fx_fl *pLeft, edge_fx_fl *pRight)
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}
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}
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static void runscanline(edge_fx_fl *left, edge_fx_fl *right)
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//runs several scanlines, until an edge is finished
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static void runscanlines(edge_fx_fl *left, edge_fx_fl *right)
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{
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//do not overstep either of the edges
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int Height = min(left->Height,right->Height);
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while(Height--) {
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hecker_DrawScanLine(left,right);
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drawscanline(left,right);
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left->Step();
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right->Step();
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}
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}
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//This function can handle a quad or a triangle. A triangle is just a quad with a duped vert.
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//rotates verts counterclockwise
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template<int type>
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inline static void rot_verts() {
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#define ROTSWAP(X) if(type>X) swap(verts[X-1],verts[X]);
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ROTSWAP(1); ROTSWAP(2); ROTSWAP(3); ROTSWAP(4);
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ROTSWAP(5); ROTSWAP(6); ROTSWAP(7);
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}
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//rotate verts until vert0.y is minimum, and then vert0.x is minimum in case of ties
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//this is a necessary precondition for our shape engine
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template<int type>
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static void sort_verts(bool backwards) {
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//if the verts are backwards, reorder them first
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if(backwards)
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for(int i=0;i<type/2;i++)
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swap(verts[i],verts[type-i-1]);
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for(;;)
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{
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//this was the only way we could get this to unroll
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#define CHECKY(X) if(type>X) if(verts[0]->y > verts[X]->y) goto doswap;
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CHECKY(1); CHECKY(2); CHECKY(3); CHECKY(4);
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CHECKY(5); CHECKY(6); CHECKY(7);
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break;
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doswap:
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rot_verts<type>();
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}
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while(verts[0]->y == verts[1]->y && verts[0]->x > verts[1]->x)
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rot_verts<type>();
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}
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//This function can handle any convex N-gon up to octagons
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//verts must be clockwise.
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//The algorithm used here is of my own devising... as far as I know.
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static void shape_engine()
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//I didnt reference anything for this algorithm but it seems like I've seen it somewhere before.
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static void shape_engine(int type, bool backwards)
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{
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failure = false;
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VERT* v[4] = {verts[0],verts[1],verts[2],verts[3]};
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//rotate verts until vert0.y is minimum, and then vert0.x is minimum in case of ties
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//this will reduce the complexity of our logic
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while(v[0]->y > v[1]->y || v[0]->y > v[2]->y || v[0]->y > v[3]->y) {
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swap(v[0],v[1]);
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swap(v[1],v[2]);
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swap(v[2],v[3]);
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}
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while(v[0]->y == v[1]->y && v[0]->x > v[1]->x) {
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swap(v[0],v[1]);
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swap(v[1],v[2]);
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swap(v[2],v[3]);
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switch(type) {
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case 3: sort_verts<3>(backwards); break;
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case 4: sort_verts<4>(backwards); break;
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case 5: sort_verts<5>(backwards); break;
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case 6: sort_verts<6>(backwards); break;
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case 7: sort_verts<7>(backwards); break;
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case 8: sort_verts<8>(backwards); break;
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default: printf("skipping type %d\n",type); return;
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}
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//we are going to step around the polygon in both directions starting from vert 0.
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//right edges will be stepped over clockwise and left edges stepped over counterclockwise.
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//these variables track that stepping, but in order to facilitate wrapping we start extra high
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//for the counter we're decrementing.
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int lv = 4, rv = 0;
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int lv = type, rv = 0;
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edge_fx_fl left, right;
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bool step_left = true, step_right = true;
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for(;;) {
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//generate new edges if necessary. we must avoid regenerating edges when they are incomplete
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//so that they can be continued on down the shape
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if(step_left) left = edge_fx_fl(v,lv&3,lv-1);
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if(step_right) right = edge_fx_fl(v,rv&3,rv+1);
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assert(rv != type);
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int _lv = lv==type?0:lv; //make sure that we ask for vert 0 when the variable contains the starting value
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if(step_left) left = edge_fx_fl(_lv,lv-1);
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if(step_right) right = edge_fx_fl(rv,rv+1);
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step_left = step_right = false;
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//handle a failure in the edge setup.
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//handle a failure in the edge setup due to nutty polys
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if(failure)
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return;
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runscanline(&left,&right);
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runscanlines(&left,&right);
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//if we ran out of an edge, step to the next one
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if(right.Height == 0) {
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step_right = true;
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rv++;
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@ -893,7 +894,7 @@ static struct TClippedPoly
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{
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int type;
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POLY* poly;
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VERT clipVerts[16]; //how many? i cant imagine having more than 6
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VERT clipVerts[MAX_CLIPPED_VERTS];
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} clippedPolys[POLYLIST_SIZE*2];
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static int clippedPolyCounter;
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@ -1035,33 +1036,22 @@ static void clipPoly(POLY* poly)
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clipPolyVsPlane(1, 1);
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clipPolyVsPlane(2, -1);
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clipPolyVsPlane(2, 1);
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//TODO - we need to parameterize back plane clipping
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if(tempClippedPoly.type < 3)
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{
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//a totally clipped poly. discard it.
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//or, a degenerate poly. we're not handling these right now
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}
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else if(tempClippedPoly.type < 5)
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else
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{
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//TODO - build right in this list instead of copying
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clippedPolys[clippedPolyCounter] = tempClippedPoly;
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clippedPolys[clippedPolyCounter].poly = poly;
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clippedPolyCounter++;
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}
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else
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{
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//turn into a triangle fan. no point even trying to make quads since those would have to get split anyway.
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//well, maybe it could end up being faster.
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for(int i=0;i<tempClippedPoly.type-2;i++)
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{
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clippedPolys[clippedPolyCounter].type = 3;
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clippedPolys[clippedPolyCounter].poly = poly;
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clippedPolys[clippedPolyCounter].clipVerts[0] = tempClippedPoly.clipVerts[0];
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clippedPolys[clippedPolyCounter].clipVerts[1] = tempClippedPoly.clipVerts[i+1];
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clippedPolys[clippedPolyCounter].clipVerts[2] = tempClippedPoly.clipVerts[i+2];
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clippedPolyCounter++;
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}
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}
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}
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static void SoftRastRender()
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@ -1128,19 +1118,15 @@ static void SoftRastRender()
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//iterate over polys
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bool needInitTexture = true;
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polynum = 0;
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for(int i=0;i<clippedPolyCounter;i++)
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{
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polynum = i;
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TClippedPoly &clippedPoly = clippedPolys[i];
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POLY *poly = clippedPoly.poly;
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int type = clippedPoly.type;
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VERT* verts[4] = {
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&clippedPoly.clipVerts[0],
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&clippedPoly.clipVerts[1],
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&clippedPoly.clipVerts[2],
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type==4?&clippedPoly.clipVerts[3]:0
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};
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VERT* verts = &clippedPoly.clipVerts[0];
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if(i == 0 || lastPolyAttr != poly->polyAttr)
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{
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@ -1152,12 +1138,12 @@ static void SoftRastRender()
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//this should be moved to gfx3d, but first we need to redo the way the lists are built
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//because it is too convoluted right now.
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//(must we throw out verts if a poly gets backface culled? if not, then it might be easier)
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//TODO - is this good enough for quads? we think so.
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//TODO - is this good enough for quads and other shapes? we think so.
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float ab[2], ac[2];
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Vector2Copy(ab, verts[1]->coord);
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Vector2Copy(ac, verts[2]->coord);
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Vector2Subtract(ab, verts[0]->coord);
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Vector2Subtract(ac, verts[0]->coord);
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Vector2Copy(ab, verts[1].coord);
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Vector2Copy(ac, verts[2].coord);
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Vector2Subtract(ab, verts[0].coord);
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Vector2Subtract(ac, verts[0].coord);
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float cross = Vector2Cross(ab, ac);
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bool backfacing = (cross<0);
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@ -1181,54 +1167,15 @@ static void SoftRastRender()
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//which is currently just a float
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for(int i=0;i<type;i++)
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for(int j=0;j<2;j++)
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verts[i]->coord[j] = iround(16.0f * verts[i]->coord[j]);
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verts[i].coord[j] = iround(16.0f * verts[i].coord[j]);
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//hmm... shader gets setup every time because it depends on sampler which may have just changed
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shader.setup(poly->polyAttr);
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//note that when we build our triangle vert lists, we reorder them for our renderer.
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//we should probably fix the renderer so we dont have to do this;
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//but then again, what does it matter?
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if(type == 4)
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{
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if(backfacing)
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{
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SubmitVertex(3,verts[0]);
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SubmitVertex(2,verts[1]);
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SubmitVertex(1,verts[2]);
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SubmitVertex(0,verts[3]);
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shape_engine();polynum++;
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}
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else
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{
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SubmitVertex(3,verts[3]);
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SubmitVertex(2,verts[2]);
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SubmitVertex(1,verts[1]);
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SubmitVertex(0,verts[0]);
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shape_engine();polynum++;
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}
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}
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else if(type == 3)
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{
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if(backfacing)
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{
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SubmitVertex(3,verts[0]);
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SubmitVertex(2,verts[0]);
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SubmitVertex(1,verts[1]);
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SubmitVertex(0,verts[2]);
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shape_engine();polynum++;
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}
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else
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{
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SubmitVertex(3,verts[2]);
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SubmitVertex(2,verts[2]);
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SubmitVertex(1,verts[1]);
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SubmitVertex(0,verts[0]);
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shape_engine();polynum++;
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}
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} else printf("skipping type %d\n",type);
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for(int i=0;i<MAX_CLIPPED_VERTS;i++)
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::verts[i] = &verts[i];
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shape_engine(type,backfacing);
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}
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// printf("rendered %d of %d polys after backface culling\n",gfx3d.polylist->count-culled,gfx3d.polylist->count);
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