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Change SoftGPU triangle rasteriser to use more standard style

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This commit is contained in:
UnknownShadow200 2024-06-05 19:04:53 +10:00
parent 74fa5daf7c
commit 8800578b65
1 changed files with 25 additions and 24 deletions
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49
src/Graphics_SoftGPU.c
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@ -321,20 +321,21 @@ static CC_INLINE int FastFloor(float value) {
return valueI > value ? valueI - 1 : valueI;
}
static void DrawTriangle(Vertex* frag1, Vertex* frag2, Vertex* frag3) {
int x1 = (int)frag1->x, y1 = (int)frag1->y;
int x2 = (int)frag2->x, y2 = (int)frag2->y;
int x3 = (int)frag3->x, y3 = (int)frag3->y;
int minX = min(x1, min(x2, x3));
int minY = min(y1, min(y2, y3));
int maxX = max(x1, max(x2, x3));
int maxY = max(y1, max(y2, y3));
#define edgeFunction(ax,ay, bx,by, cx,cy) ((bx - ax) * (cy - ay) - (by - ay) * (cx - ax))
// TODO backface culling
static void DrawTriangle(Vertex* V0, Vertex* V1, Vertex* V2) {
int x0 = (int)V0->x, y0 = (int)V0->y;
int x1 = (int)V1->x, y1 = (int)V1->y;
int x2 = (int)V2->x, y2 = (int)V2->y;
int minX = min(x0, min(x1, x2));
int minY = min(y0, min(y1, y2));
int maxX = max(x0, max(x1, x2));
int maxY = max(y0, max(y1, y2));
int area = edgeFunction(x0,y0, x1,y1, x2,y2);
if (faceCulling) {
// https://gamedev.stackexchange.com/questions/203694/how-to-make-backface-culling-work-correctly-in-both-orthographic-and-perspective
int sign = (x2 - x1) * (y3 - y1) - (x3 - x1) * (y2 - y1);
if (sign > 0) return;
if (area > 0) return;
}
// Reject triangles completely outside
@ -346,32 +347,32 @@ static void DrawTriangle(Vertex* frag1, Vertex* frag2, Vertex* frag3) {
minY = max(minY, 0); maxY = min(maxY, fb_maxY);
// NOTE: W in frag variables below is actually 1/W
float factor = 1.0f / ((y2 - y3) * (x1 - x3) + (x3 - x2) * (y1 - y3));
float w1 = frag1->w, w2 = frag2->w, w3 = frag3->w;
float factor = 1.0f / area;
float w0 = V0->w, w1 = V1->w, w2 = V2->w;
// TODO proper clipping
if (w1 <= 0 || w2 <= 0 || w3 <= 0) return;
if (w0 <= 0 || w1 <= 0 || w2 <= 0) return;
float z1 = frag1->z, z2 = frag2->z, z3 = frag3->z;
float u1 = frag1->u, u2 = frag2->u, u3 = frag3->u;
float v1 = frag1->v, v2 = frag2->v, v3 = frag3->v;
PackedCol color = frag1->c;
float z0 = V0->z, z1 = V1->z, z2 = V2->z;
float u0 = V0->u, u1 = V1->u, u2 = V2->u;
float v0 = V0->v, v1 = V1->v, v2 = V2->v;
PackedCol color = V0->c;
for (int y = minY; y <= maxY; y++) {
float yy = y + 0.5f;
for (int x = minX; x <= maxX; x++) {
float xx = x + 0.5f;
float ic0 = ((y2 - y3) * (xx - x3) + (x3 - x2) * (yy - y3)) * factor;
float ic0 = ((y1 - y2) * (xx - x2) + (x2 - x1) * (yy - y2)) * factor;
if (ic0 < 0 || ic0 > 1) continue;
float ic1 = ((y3 - y1) * (xx - x3) + (x1 - x3) * (yy - y3)) * factor;
float ic1 = ((y2 - y0) * (xx - x2) + (x0 - x2) * (yy - y2)) * factor;
if (ic1 < 0 || ic1 > 1) continue;
float ic2 = 1.0f - ic0 - ic1;
if (ic2 < 0 || ic2 > 1) continue;
int index = y * fb_width + x;
float w = 1 / (ic0 * w1 + ic1 * w2 + ic2 * w3);
float z = (ic0 * z1 + ic1 * z2 + ic2 * z3) * w;
float w = 1 / (ic0 * w0 + ic1 * w1 + ic2 * w2);
float z = (ic0 * z0 + ic1 * z1 + ic2 * z2) * w;
if (depthTest && (z < 0 || z > depthBuffer[index])) continue;
if (!colWrite) {
@ -381,8 +382,8 @@ static void DrawTriangle(Vertex* frag1, Vertex* frag2, Vertex* frag3) {
int R, G, B, A;
if (gfx_format == VERTEX_FORMAT_TEXTURED) {
float u = (ic0 * u1 + ic1 * u2 + ic2 * u3) * w;
float v = (ic0 * v1 + ic1 * v2 + ic2 * v3) * w;
float u = (ic0 * u0 + ic1 * u1 + ic2 * u2) * w;
float v = (ic0 * v0 + ic1 * v1 + ic2 * v2) * w;
int texX = ((int)(Math_AbsF(u - FastFloor(u)) * curTexWidth )) & texWidthMask;
int texY = ((int)(Math_AbsF(v - FastFloor(v)) * curTexHeight)) & texHeightMask;
int texIndex = texY * curTexWidth + texX;