GSdx-hw: Add automatic detection of half-bottom in TS

Typical shuffle case is 1/2 height so other half is undesired

In dbz we split the depth buffer.
- Sample first half, write to `0x0`.
- Sample second half, write to `0x800`
- Finally, sample `0x0` though `0xffc`

Crash Twinsanity is a similar case.

plugins/GSdx/Renderers/HW/GSRendererHW.cpp

@@ -448,6 +448,20 @@ void GSRendererHW::ConvertSpriteTextureShuffle(bool& write_ba, bool& read_ba)
 	tex_pos &= 0xFF;
 	read_ba = (tex_pos > 112 && tex_pos < 144);
 
+	// Here's the idea
+	// TS effect is 16 bits but we emulate it on a 32 bits format
+	// Normally this means we need to divide size by 2.
+	//
+	// Some games do two TS effects on each half of the buffer.
+	// This makes a mess for us in the TC because we end up with two targets
+	// when we only want one, thus half screen bug.
+	//
+	// 32bits emulation means we can do the effect once but double the size.
+	// Test cases: Crash Twinsantiy and DBZ BT3
+	int height_delta = m_src->m_valid_rect.height() - m_r.height();
+	// Test Case: NFS: HP2 splits the effect h:256 and h:192 so 64
+	bool half_bottom = abs(height_delta) <= 64;
+
 	if (PRIM->FST) {
 		GL_INS("First vertex is  P: %d => %d    T: %d => %d", v[0].XYZ.X, v[1].XYZ.X, v[0].U, v[1].U);
 
@@ -462,6 +476,7 @@ void GSRendererHW::ConvertSpriteTextureShuffle(bool& write_ba, bool& read_ba)
 			else
 				v[i+1].U     += 128u;
 
+			if (!half_bottom){
 				// Height is too big (2x).
 				int tex_offset = v[i].V & 0xF;
 				GSVector4i offset(o.OFY, tex_offset, o.OFY, tex_offset);
@@ -474,6 +489,7 @@ void GSRendererHW::ConvertSpriteTextureShuffle(bool& write_ba, bool& read_ba)
 				v[i + 1].XYZ.Y = (uint16)tmp.z;
 				v[i + 1].V = (uint16)tmp.w;
 			}
+		}
 	} else {
 		const float offset_8pix = 8.0f / tw;
 		GL_INS("First vertex is  P: %d => %d    T: %f => %f (offset %f)", v[0].XYZ.X, v[1].XYZ.X, v[0].ST.S, v[1].ST.S, offset_8pix);
@@ -489,6 +505,7 @@ void GSRendererHW::ConvertSpriteTextureShuffle(bool& write_ba, bool& read_ba)
 			else
 				v[i+1].ST.S  += offset_8pix;
 
+			if (!half_bottom) {
 				// Height is too big (2x).
 				GSVector4i offset(o.OFY, o.OFY);
 
@@ -502,6 +519,7 @@ void GSRendererHW::ConvertSpriteTextureShuffle(bool& write_ba, bool& read_ba)
 				v[i + 1].ST.T /= 2.0f;
 			}
 		}
+	}
 
 	// Update vertex trace too. Avoid issue to compute bounding box
 	if (write_ba)
@@ -509,18 +527,21 @@ void GSRendererHW::ConvertSpriteTextureShuffle(bool& write_ba, bool& read_ba)
 	else
 		m_vt.m_max.p.x += 8.0f;
 
-
+	if (!half_bottom) {
 		float delta_Y = m_vt.m_max.p.y - m_vt.m_min.p.y;
 		m_vt.m_max.p.y -= delta_Y / 2.0f;
+	}
 
 	if (read_ba)
 		m_vt.m_min.t.x -= 8.0f;
 	else
 		m_vt.m_max.t.x += 8.0f;
 
+	if (!half_bottom) {
 		float delta_T = m_vt.m_max.t.y - m_vt.m_min.t.y;
 		m_vt.m_max.t.y -= delta_T / 2.0f;
 	}
+}
 
 GSVector4 GSRendererHW::RealignTargetTextureCoordinate(const GSTextureCache::Source* tex)
 {