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OpenGL Renderer: Bring back support for handling the transparent polygon ID check. This fixes many graphical glitches involving transparent polygons in many games. (Regression from r5372. Fixes #74 and fixes #24.)

This commit is contained in:
rogerman 2017-10-13 18:35:05 -07:00
parent 9bfbaf23b8
commit 73b5074313
2 changed files with 213 additions and 84 deletions
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251
desmume/src/OGLRender.cpp
View File

@ -1668,10 +1668,14 @@ Render3DError OpenGLRenderer::DrawAlphaTexturePolygon(const GLenum polyPrimitive
glStencilOp(GL_ZERO, GL_ZERO, GL_REPLACE);
glStencilMask(0x80);
glUniform1i(OGLRef.uniformTexDrawOpaque, GL_FALSE);
glDrawElements(polyPrimitive, vertIndexCount, GL_UNSIGNED_SHORT, indexBufferPtr);
if (canHaveOpaqueFragments)
{
glUniform1i(OGLRef.uniformTexDrawOpaque, GL_TRUE);
glDrawElements(polyPrimitive, vertIndexCount, GL_UNSIGNED_SHORT, indexBufferPtr);
glUniform1i(OGLRef.uniformTexDrawOpaque, GL_FALSE);
}
// Use the stencil buffer to determine which fragments pass the higher-side tolerance.
glUniform1i(OGLRef.uniformPolyDepthOffsetMode, 2);
@ -1680,38 +1684,66 @@ Render3DError OpenGLRenderer::DrawAlphaTexturePolygon(const GLenum polyPrimitive
glStencilOp(GL_ZERO, GL_ZERO, GL_KEEP);
glStencilMask(0x80);
glUniform1i(OGLRef.uniformTexDrawOpaque, GL_FALSE);
glDrawElements(polyPrimitive, vertIndexCount, GL_UNSIGNED_SHORT, indexBufferPtr);
if (canHaveOpaqueFragments)
{
glUniform1i(OGLRef.uniformTexDrawOpaque, GL_TRUE);
glDrawElements(polyPrimitive, vertIndexCount, GL_UNSIGNED_SHORT, indexBufferPtr);
glUniform1i(OGLRef.uniformTexDrawOpaque, GL_FALSE);
}
// Set up the actual drawing of the polygon, using the mask within the stencil buffer to determine which fragments should pass.
glUniform1i(OGLRef.uniformPolyDepthOffsetMode, 0);
glColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);
glDepthFunc(GL_ALWAYS);
glStencilFunc(GL_EQUAL, 0x80 | opaquePolyID, 0x80);
glStencilMask(0x7F); // Drawing non-shadow polygons will implicitly reset the shadow volume mask.
// First do the transparent polygon ID check for the translucent fragments.
glStencilFunc(GL_NOTEQUAL, 0x40 | opaquePolyID, 0x7F);
glStencilOp(GL_ZERO, GL_ZERO, GL_KEEP);
glStencilMask(0x80);
glDrawElements(polyPrimitive, vertIndexCount, GL_UNSIGNED_SHORT, indexBufferPtr);
// Draw the translucent fragments.
glStencilOp(GL_KEEP, GL_KEEP, GL_KEEP);
glStencilFunc(GL_EQUAL, 0xC0 | opaquePolyID, 0x80);
glStencilOp(GL_KEEP, GL_KEEP, GL_REPLACE);
glStencilMask(0x7F);
glColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);
glDepthMask((enableAlphaDepthWrite) ? GL_TRUE : GL_FALSE);
glUniform1i(OGLRef.uniformTexDrawOpaque, GL_FALSE);
glDrawElements(polyPrimitive, vertIndexCount, GL_UNSIGNED_SHORT, indexBufferPtr);
// Draw the opaque fragments if they might exist.
if (canHaveOpaqueFragments)
{
glStencilOp(GL_KEEP, GL_KEEP, GL_REPLACE);
glStencilFunc(GL_EQUAL, 0x80 | opaquePolyID, 0x80);
glDepthMask(GL_TRUE);
glUniform1i(OGLRef.uniformTexDrawOpaque, GL_TRUE);
glDrawElements(polyPrimitive, vertIndexCount, GL_UNSIGNED_SHORT, indexBufferPtr);
glUniform1i(OGLRef.uniformTexDrawOpaque, GL_FALSE);
glStencilOp(GL_KEEP, GL_KEEP, GL_KEEP);
glDepthMask((enableAlphaDepthWrite) ? GL_TRUE : GL_FALSE);
}
// Clear bit 7 (0x80) now so that future polygons don't get confused.
glStencilFunc(GL_ALWAYS, 0x80, 0x80);
glStencilOp(GL_KEEP, GL_KEEP, GL_ZERO);
glStencilMask(0x80);
glColorMask(GL_FALSE, GL_FALSE, GL_FALSE, GL_FALSE);
glDepthMask(GL_FALSE);
glDrawElements(polyPrimitive, vertIndexCount, GL_UNSIGNED_SHORT, indexBufferPtr);
if (canHaveOpaqueFragments)
{
glUniform1i(OGLRef.uniformTexDrawOpaque, GL_TRUE);
glDrawElements(polyPrimitive, vertIndexCount, GL_UNSIGNED_SHORT, indexBufferPtr);
glUniform1i(OGLRef.uniformTexDrawOpaque, GL_FALSE);
}
// Finally, reset the rendering states.
glStencilFunc(GL_NOTEQUAL, 0x40 | opaquePolyID, 0x7F);
glStencilOp(GL_KEEP, GL_KEEP, GL_REPLACE);
glStencilMask(0xFF);
glColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);
glDepthMask((enableAlphaDepthWrite) ? GL_TRUE : GL_FALSE);
}
else
{
@ -1739,16 +1771,31 @@ Render3DError OpenGLRenderer::DrawAlphaTexturePolygon(const GLenum polyPrimitive
// Set up the actual drawing of the polygon, using the mask within the stencil buffer to determine which fragments should pass.
glUniform1i(OGLRef.uniformPolyDepthOffsetMode, 0);
glColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);
glDepthMask(GL_TRUE);
glDepthFunc(GL_ALWAYS);
glStencilFunc(GL_EQUAL, 0x80 | opaquePolyID, 0x80);
glStencilMask(0x7F); // Drawing non-shadow polygons will implicitly reset the shadow volume mask.
glStencilOp(GL_KEEP, GL_KEEP, GL_REPLACE);
glDepthMask(GL_TRUE);
glStencilMask(0x7F);
// Draw the polygon as completely opaque.
glDrawElements(polyPrimitive, vertIndexCount, GL_UNSIGNED_SHORT, indexBufferPtr);
// Clear bit 7 (0x80) now so that future polygons don't get confused.
glColorMask(GL_FALSE, GL_FALSE, GL_FALSE, GL_FALSE);
glDepthMask(GL_FALSE);
glStencilFunc(GL_ALWAYS, 0x80, 0x80);
glStencilOp(GL_KEEP, GL_KEEP, GL_ZERO);
glStencilMask(0x80);
glDrawElements(polyPrimitive, vertIndexCount, GL_UNSIGNED_SHORT, indexBufferPtr);
// Finally, reset the rendering states.
glStencilFunc(GL_ALWAYS, opaquePolyID, 0x3F);
glStencilOp(GL_KEEP, GL_KEEP, GL_REPLACE);
glStencilMask(0xFF);
glColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);
glDepthMask(GL_TRUE);
glUniform1i(OGLRef.uniformTexDrawOpaque, GL_FALSE);
}
}
@ -1764,6 +1811,7 @@ Render3DError OpenGLRenderer::DrawAlphaTexturePolygon(const GLenum polyPrimitive
{
if (DRAWMODE != OGLPolyDrawMode_ZeroAlphaPass)
{
glStencilFunc(GL_ALWAYS, opaquePolyID, 0x3F);
glStencilOp(GL_KEEP, GL_KEEP, GL_REPLACE);
glDepthMask(GL_TRUE);
}
@ -1774,7 +1822,8 @@ Render3DError OpenGLRenderer::DrawAlphaTexturePolygon(const GLenum polyPrimitive
if (DRAWMODE != OGLPolyDrawMode_ZeroAlphaPass)
{
glStencilOp(GL_KEEP, GL_KEEP, GL_KEEP);
glStencilFunc(GL_NOTEQUAL, 0x40 | opaquePolyID, 0x7F);
glStencilOp(GL_KEEP, GL_KEEP, GL_REPLACE);
glDepthMask((enableAlphaDepthWrite) ? GL_TRUE : GL_FALSE);
}
}
@ -1822,16 +1871,51 @@ Render3DError OpenGLRenderer::DrawOtherPolygon(const GLenum polyPrimitive, const
glStencilMask(0x80);
glDrawElements(polyPrimitive, vertIndexCount, GL_UNSIGNED_SHORT, indexBufferPtr);
// Set up the actual drawing of the polygon.
glUniform1i(OGLRef.uniformPolyDepthOffsetMode, 0);
glDepthFunc(GL_ALWAYS);
// If this is a transparent polygon, then we need to do the transparent polygon ID check.
if (DRAWMODE == OGLPolyDrawMode_DrawTranslucentPolys)
{
glStencilFunc(GL_NOTEQUAL, 0x40 | opaquePolyID, 0x7F);
glStencilOp(GL_ZERO, GL_ZERO, GL_KEEP);
glStencilMask(0x80);
glDrawElements(polyPrimitive, vertIndexCount, GL_UNSIGNED_SHORT, indexBufferPtr);
}
// Draw the polygon using the mask within the stencil buffer to determine which fragments should pass.
glColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);
glDepthMask(((DRAWMODE == OGLPolyDrawMode_DrawOpaquePolys) || enableAlphaDepthWrite) ? GL_TRUE : GL_FALSE);
glUniform1i(OGLRef.uniformPolyDepthOffsetMode, 0);
glDepthFunc(GL_ALWAYS);
glStencilFunc(GL_EQUAL, 0x80 | opaquePolyID, 0x80);
glStencilOp(GL_KEEP, GL_KEEP, (DRAWMODE == OGLPolyDrawMode_DrawTranslucentPolys) ? GL_KEEP : GL_REPLACE);
glStencilMask(0x7F); // Drawing non-shadow polygons will implicitly reset the shadow volume mask.
glStencilFunc(GL_EQUAL, (DRAWMODE == OGLPolyDrawMode_DrawTranslucentPolys) ? 0xC0 | opaquePolyID : 0x80 | opaquePolyID, 0x80);
glStencilOp(GL_KEEP, GL_KEEP, GL_REPLACE);
glStencilMask(0x7F);
glDrawElements(polyPrimitive, vertIndexCount, GL_UNSIGNED_SHORT, indexBufferPtr);
// Clear bit 7 (0x80) now so that future polygons don't get confused.
glColorMask(GL_FALSE, GL_FALSE, GL_FALSE, GL_FALSE);
glDepthMask(GL_FALSE);
glStencilFunc(GL_ALWAYS, 0x80, 0x80);
glStencilOp(GL_KEEP, GL_KEEP, GL_ZERO);
glStencilMask(0x80);
glDrawElements(polyPrimitive, vertIndexCount, GL_UNSIGNED_SHORT, indexBufferPtr);
// Finally, reset the rendering states.
if (DRAWMODE == OGLPolyDrawMode_DrawTranslucentPolys)
{
glStencilFunc(GL_NOTEQUAL, 0x40 | opaquePolyID, 0x7F);
}
else
{
glStencilFunc(GL_ALWAYS, opaquePolyID, 0x3F);
}
glStencilOp(GL_KEEP, GL_KEEP, GL_REPLACE);
glStencilMask(0xFF);
glColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);
glDepthMask(((DRAWMODE == OGLPolyDrawMode_DrawOpaquePolys) || enableAlphaDepthWrite) ? GL_TRUE : GL_FALSE);
}
else
{
@ -4265,31 +4349,51 @@ Render3DError OpenGLRenderer_1_2::SetupPolygon(const POLY &thePoly, bool treatAs
// Set up shadow polygon states.
//
// See comments in DrawShadowPolygon() for more information about
// how this 4-pass process works in OpenGL.
// how this 5-pass process works in OpenGL.
if (thePoly.attribute.PolygonID == 0)
{
// 1st pass: Use stencil buffer bit 6 (0x40) for the shadow volume mask.
// 1st pass: Use stencil buffer bit 7 (0x80) for the shadow volume mask.
// Write only on depth-fail.
glStencilFunc(GL_ALWAYS, 0x40, 0x40);
glStencilFunc(GL_ALWAYS, 0x80, 0x80);
glStencilOp(GL_KEEP, GL_REPLACE, GL_KEEP);
glStencilMask(0x40);
glStencilMask(0x80);
}
else
{
// 2nd pass: Compare stencil buffer bits 0-5 (0x3F) with this polygon's ID. If this stencil
// test fails, remove the fragment from the shadow volume mask by clearing bit 6.
// test fails, remove the fragment from the shadow volume mask by clearing bit 7.
glStencilFunc(GL_NOTEQUAL, thePoly.attribute.PolygonID, 0x3F);
glStencilOp(GL_ZERO, GL_KEEP, GL_KEEP);
glStencilMask(0x40);
glStencilMask(0x80);
}
glColorMask(GL_FALSE, GL_FALSE, GL_FALSE, GL_FALSE);
glDepthMask(GL_FALSE);
}
else
{
// Polygon IDs are always written for every polygon, whether they are opaque or transparent, just as
// long as they pass the stencil and depth tests.
// - Polygon IDs are contained in stencil bits 0-5 (0x3F).
// - The translucent fragment flag is contained in stencil bit 6 (0x40).
//
// Opaque polygons have no stencil conditions, so if they pass the depth test, then they write out
// their polygon ID with a translucent fragment flag of 0.
//
// Transparent polygons have the stencil condition where they will not draw if they are drawing on
// top of previously drawn translucent fragments with the same polygon ID. This condition is checked
// using both polygon ID bits and the translucent fragment flag. If the polygon passes both stencil
// and depth tests, it writes out its polygon ID with a translucent fragment flag of 1.
if (treatAsTranslucent)
{
glStencilFunc(GL_NOTEQUAL, 0x40 | thePoly.attribute.PolygonID, 0x7F);
}
else
{
glStencilFunc(GL_ALWAYS, thePoly.attribute.PolygonID, 0x3F);
glStencilOp(GL_KEEP, GL_KEEP, (treatAsTranslucent) ? GL_KEEP : GL_REPLACE);
}
glStencilOp(GL_KEEP, GL_KEEP, GL_REPLACE);
glStencilMask(0xFF); // Drawing non-shadow polygons will implicitly reset the shadow volume mask.
glColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);
@ -4409,24 +4513,34 @@ Render3DError OpenGLRenderer_1_2::DrawShadowPolygon(const GLenum polyPrimitive,
// Note that the 1st and 2nd passes are performed using states from SetupPolygon().
//
// 1st pass (NDS driven): The NDS creates the shadow volume and updates only the
// stencil buffer, writing to bit 6 (0x40). Color and depth writes are disabled for this
// stencil buffer, writing to bit 7 (0x80). Color and depth writes are disabled for this
// pass.
//
// 2nd pass (NDS driven): Normally, stencil buffer bits marked for shadow rendering
// are supposed to be drawn in this step, but there is an additional polygon ID check
// that has to be made before writing out the fragment. Since OpenGL can only do
// one type of stencil buffer check at a time, we need to do things differently from
// what the NDS does at this point. In OpenGL, this pass is used only to update the
// stencil buffer for the polygon ID check, checking bits 0x3F for the polygon ID,
// and clearing bit 6 (0x40) if this check fails. Color and depth writes are disabled
// are supposed to be drawn in this step, but there are additional checks that need to
// be made before writing out the fragment. Since OpenGL can only do one type of stencil
// buffer check at a time, we need to do things differently from what the NDS does at
// this point.
//
// 3rd pass (emulator driven): This pass only occurs when the shadow polygon is opaque.
// Since opaque polygons need to update their polygon IDs, we update only the stencil
// buffer with the polygon ID. Color and depth writes are disabled for this pass.
// for this pass.
// In OpenGL, this pass is used only to update the stencil buffer for the polygon
// ID check, checking bits 0x3F for the polygon ID, and clearing bit 7 (0x80) if this
// check fails. Color and depth writes are disabled
//
// 4th pass (emulator driven): Use stencil buffer bit 6 (0x40) for the shadow volume
// mask and render the shadow polygons only within the mask. Color writes are always
// 3rd pass (emulator driven): This pass only occurs when the shadow polygon is
// transparent, which is the typical case. Since transparent polygons have a rule for
// which they cannot draw fragments on top of previously drawn translucent fragments with
// the same polygon IDs, we also need to do an additional polygon ID check to ensure that
// it isn't a transparent polygon ID. We continue to check bits 0x3F for the polygon ID,
// in addition to also checking the translucent fragment flag at bit 6 (0x40). If this
// check fails, then bit 7 (0x80) is cleared. Color and depth writes are disabled for this
// pass.
//
// 4th pass (emulator driven): Use stencil buffer bit 7 (0x70) for the shadow volume
// mask and write out the polygon ID and translucent fragment flag only to those fragments
// within the mask. Color and depth writes are disabled for this pass.
//
// 5th pass (emulator driven): Use stencil buffer bit 7 (0x70) for the shadow volume
// mask and draw the shadow polygon fragments only within the mask. Color writes are always
// enabled and depth writes are enabled if the shadow polygon is opaque or if transparent
// polygon depth writes are enabled.
@ -4435,28 +4549,20 @@ Render3DError OpenGLRenderer_1_2::DrawShadowPolygon(const GLenum polyPrimitive,
{
if (performDepthEqualTest && this->isShaderSupported)
{
// Use the stencil buffer to determine which fragments pass the lower-side tolerance.
// Use the stencil buffer to determine which fragments fail the depth test using the lower-side tolerance.
glUniform1i(OGLRef.uniformPolyDepthOffsetMode, 1);
glDepthFunc(GL_LEQUAL);
glStencilFunc(GL_ALWAYS, 0x80, 0x80);
glStencilOp(GL_ZERO, GL_ZERO, GL_REPLACE);
glStencilOp(GL_KEEP, GL_REPLACE, GL_KEEP);
glStencilMask(0x80);
glDrawElements(polyPrimitive, vertIndexCount, GL_UNSIGNED_SHORT, indexBufferPtr);
// Use the stencil buffer to determine which fragments pass the higher-side tolerance.
// Use the stencil buffer to determine which fragments fail the depth test using the higher-side tolerance.
glUniform1i(OGLRef.uniformPolyDepthOffsetMode, 2);
glDepthFunc(GL_GEQUAL);
glStencilFunc(GL_EQUAL, 0x80, 0x80);
glStencilOp(GL_ZERO, GL_ZERO, GL_KEEP);
glStencilMask(0x80);
glDrawElements(polyPrimitive, vertIndexCount, GL_UNSIGNED_SHORT, indexBufferPtr);
// Draw the polygon using the mask within the stencil buffer to determine which fragments should pass.
glUniform1i(OGLRef.uniformPolyDepthOffsetMode, 0);
glDepthFunc(GL_ALWAYS);
glStencilFunc(GL_EQUAL, 0xC0, 0x80);
glStencilFunc(GL_NOTEQUAL, 0x80, 0x80);
glStencilOp(GL_KEEP, GL_REPLACE, GL_KEEP);
glStencilMask(0x40);
glStencilMask(0x80);
glDrawElements(polyPrimitive, vertIndexCount, GL_UNSIGNED_SHORT, indexBufferPtr);
}
else
@ -4473,8 +4579,8 @@ Render3DError OpenGLRenderer_1_2::DrawShadowPolygon(const GLenum polyPrimitive,
// Use the stencil buffer to determine which fragments pass the lower-side tolerance.
glUniform1i(OGLRef.uniformPolyDepthOffsetMode, 1);
glDepthFunc(GL_LEQUAL);
glStencilFunc(GL_ALWAYS, 0x80, 0x80);
glStencilOp(GL_ZERO, GL_ZERO, GL_REPLACE);
glStencilFunc(GL_EQUAL, 0x80, 0x80);
glStencilOp(GL_ZERO, GL_ZERO, GL_KEEP);
glStencilMask(0x80);
glDrawElements(polyPrimitive, vertIndexCount, GL_UNSIGNED_SHORT, indexBufferPtr);
@ -4490,13 +4596,9 @@ Render3DError OpenGLRenderer_1_2::DrawShadowPolygon(const GLenum polyPrimitive,
// Fragments that fail this stencil test are removed from the shadow volume mask.
glUniform1i(OGLRef.uniformPolyDepthOffsetMode, 0);
glDepthFunc(GL_ALWAYS);
glStencilFunc(GL_EQUAL, 0xC0, 0xC0);
glStencilOp(GL_ZERO, GL_KEEP, GL_KEEP);
glStencilMask(0x40);
glDrawElements(polyPrimitive, vertIndexCount, GL_UNSIGNED_SHORT, indexBufferPtr);
// Set up the polygon ID check as normal.
glStencilFunc(GL_NOTEQUAL, opaquePolyID, 0x3F);
glStencilOp(GL_ZERO, GL_ZERO, GL_KEEP);
glStencilMask(0x80);
glDrawElements(polyPrimitive, vertIndexCount, GL_UNSIGNED_SHORT, indexBufferPtr);
}
else
@ -4504,22 +4606,29 @@ Render3DError OpenGLRenderer_1_2::DrawShadowPolygon(const GLenum polyPrimitive,
glDrawElements(polyPrimitive, vertIndexCount, GL_UNSIGNED_SHORT, indexBufferPtr);
}
// 3rd pass: Update the polygon IDs in the stencil buffer if the shadow polygons are opaque.
if (!isTranslucent)
// 3rd pass: Do the transparent polygon ID check. For transparent shadow polygons, we need to
// also ensure that we're not drawing over translucent fragments with the same polygon IDs.
if (isTranslucent)
{
glStencilFunc(GL_EQUAL, 0x40 | opaquePolyID, 0x40);
glStencilOp(GL_KEEP, GL_KEEP, GL_REPLACE);
glStencilMask(0x3F);
glStencilFunc(GL_NOTEQUAL, 0xC0 | opaquePolyID, 0x7F);
glStencilOp(GL_ZERO, GL_KEEP, GL_KEEP);
glStencilMask(0x80);
glDrawElements(polyPrimitive, vertIndexCount, GL_UNSIGNED_SHORT, indexBufferPtr);
}
// 4th pass: Draw the shadow polygon.
glStencilFunc(GL_EQUAL, 0x40, 0x40);
// 4th pass: Update the polygon IDs in the stencil buffer.
glStencilFunc(GL_EQUAL, (isTranslucent) ? 0xC0 | opaquePolyID : 0x80 | opaquePolyID, 0x80);
glStencilOp(GL_KEEP, GL_KEEP, GL_REPLACE);
glStencilMask(0x7F);
glDrawElements(polyPrimitive, vertIndexCount, GL_UNSIGNED_SHORT, indexBufferPtr);
// 5th pass: Draw the shadow polygon.
glStencilFunc(GL_EQUAL, 0x80, 0x80);
// Technically, a depth-fail result should also clear the shadow volume mask, but
// Mario Kart DS draws shadow polygons better when it doesn't clear bits on depth-fail.
// I have no idea why this works. - rogerman 2016/12/21
glStencilOp(GL_ZERO, GL_KEEP, GL_ZERO);
glStencilMask(0x40);
glStencilMask(0x80);
glColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);
glDepthMask((!isTranslucent || enableAlphaDepthWrite) ? GL_TRUE : GL_FALSE);
@ -4537,7 +4646,7 @@ Render3DError OpenGLRenderer_1_2::DrawShadowPolygon(const GLenum polyPrimitive,
// Reset the OpenGL states back to their original shadow polygon states.
glStencilFunc(GL_NOTEQUAL, opaquePolyID, 0x3F);
glStencilOp(GL_ZERO, GL_KEEP, GL_KEEP);
glStencilMask(0x40);
glStencilMask(0x80);
glColorMask(GL_FALSE, GL_FALSE, GL_FALSE, GL_FALSE);
glDepthMask(GL_FALSE);

34
desmume/src/OGLRender_3_2.cpp
View File

@ -1889,31 +1889,51 @@ Render3DError OpenGLRenderer_3_2::SetupPolygon(const POLY &thePoly, bool treatAs
// Set up shadow polygon states.
//
// See comments in DrawShadowPolygon() for more information about
// how this 4-pass process works in OpenGL.
// how this 5-pass process works in OpenGL.
if (thePoly.attribute.PolygonID == 0)
{
// 1st pass: Use stencil buffer bit 6 (0x40) for the shadow volume mask.
// 1st pass: Use stencil buffer bit 7 (0x80) for the shadow volume mask.
// Write only on depth-fail.
glStencilFunc(GL_ALWAYS, 0x40, 0x40);
glStencilFunc(GL_ALWAYS, 0x80, 0x80);
glStencilOp(GL_KEEP, GL_REPLACE, GL_KEEP);
glStencilMask(0x40);
glStencilMask(0x80);
}
else
{
// 2nd pass: Compare stencil buffer bits 0-5 (0x3F) with this polygon's ID. If this stencil
// test fails, remove the fragment from the shadow volume mask by clearing bit 6.
// test fails, remove the fragment from the shadow volume mask by clearing bit 7.
glStencilFunc(GL_NOTEQUAL, thePoly.attribute.PolygonID, 0x3F);
glStencilOp(GL_ZERO, GL_KEEP, GL_KEEP);
glStencilMask(0x40);
glStencilMask(0x80);
}
glColorMask(GL_FALSE, GL_FALSE, GL_FALSE, GL_FALSE);
glDepthMask(GL_FALSE);
}
else
{
// Polygon IDs are always written for every polygon, whether they are opaque or transparent, just as
// long as they pass the stencil and depth tests.
// - Polygon IDs are contained in stencil bits 0-5 (0x3F).
// - The translucent fragment flag is contained in stencil bit 6 (0x40).
//
// Opaque polygons have no stencil conditions, so if they pass the depth test, then they write out
// their polygon ID with a translucent fragment flag of 0.
//
// Transparent polygons have the stencil condition where they will not draw if they are drawing on
// top of previously drawn translucent fragments with the same polygon ID. This condition is checked
// using both polygon ID bits and the translucent fragment flag. If the polygon passes both stencil
// and depth tests, it writes out its polygon ID with a translucent fragment flag of 1.
if (treatAsTranslucent)
{
glStencilFunc(GL_NOTEQUAL, 0x40 | thePoly.attribute.PolygonID, 0x7F);
}
else
{
glStencilFunc(GL_ALWAYS, thePoly.attribute.PolygonID, 0x3F);
glStencilOp(GL_KEEP, GL_KEEP, (treatAsTranslucent) ? GL_KEEP : GL_REPLACE);
}
glStencilOp(GL_KEEP, GL_KEEP, GL_REPLACE);
glStencilMask(0xFF); // Drawing non-shadow polygons will implicitly reset the shadow volume mask.
glColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);