Implement logic for dropping invisible triangles from the strip
This commit is contained in:
Luke Benstead
parent
e8e0881db8
commit
299df08111
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@ -47,7 +47,7 @@ TriangleClipResult clipTriangleToNearZ(
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*/
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typedef unsigned char uint8;
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uint8 visible = (v1->z >= plane_dist) ? 1 : 0 | (v2->z >= plane_dist) ? 2 : 0 | (v3->z >= plane_dist) ? 4 : 0;
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uint8 visible = ((v1->z <= -plane_dist) ? 1 : 0) | ((v2->z <= -plane_dist) ? 2 : 0) | ((v3->z <= -plane_dist) ? 4 : 0);
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switch(visible) {
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case 0b000:
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@ -69,8 +69,6 @@ TriangleClipResult clipTriangleToNearZ(
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default: {
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/* One vertex is visible */
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/* This is the "easy" case, we simply find the vertex which is visible, and clip the lines to the other 2 against the plane */
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fprintf(stderr, "Clipping triangle\n");
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pvr_vertex_t tmp1, tmp2;
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float t1, t2;
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120
GL/draw.c
120
GL/draw.c
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@ -213,8 +213,10 @@ static void submitVertices(GLenum mode, GLsizei first, GLsizei count, GLenum typ
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// with the additional space for the header.
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GLsizei start_of_output = activePolyList()->vector.size + 1;
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AlignedVector* list_vector = &activePolyList()->vector;
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// Make room for the element + the header
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PVRCommand* dst = (PVRCommand*) aligned_vector_extend(&activePolyList()->vector, count + 1);
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PVRCommand* dst = (PVRCommand*) aligned_vector_extend(list_vector, count + 1);
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// Store a pointer to the header
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pvr_poly_hdr_t* hdr = (pvr_poly_hdr_t*) dst;
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@ -256,8 +258,8 @@ static void submitVertices(GLenum mode, GLsizei first, GLsizei count, GLenum typ
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}
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aligned_vector_resize(&w_coordinates, 0);
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struct {
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pvr_vertex_t* vout[3];
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static struct {
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pvr_vertex_t* vin[3];
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GLfloat w[3];
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GLubyte vcount;
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} Triangle;
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@ -265,7 +267,7 @@ static void submitVertices(GLenum mode, GLsizei first, GLsizei count, GLenum typ
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Triangle.vcount = 0;
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/* Loop 1. Calculate vertex colours, transform, but don't apply perspective division */
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for(rel = 0, i = first; i < count; ++i, ++rel) {
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for(rel = 0, i = first; i < count; ++i, ++rel) {
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pvr_vertex_t* vertex = (pvr_vertex_t*) dst;
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vertex->u = vertex->v = 0.0f;
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vertex->argb = 0;
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@ -344,14 +346,116 @@ static void submitVertices(GLenum mode, GLsizei first, GLsizei count, GLenum typ
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aligned_vector_push_back(&w_coordinates, &W, 1);
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Triangle.w[Triangle.vcount] = W;
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Triangle.vout[Triangle.vcount] = vertex;
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Triangle.vin[Triangle.vcount] = vertex;
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Triangle.vcount++;
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if(Triangle.vcount == 3) {
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pvr_vertex_t clipped[4];
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/* OK we have a whole triangle, we may have to clip */
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TriangleClipResult tri_result = clipTriangleToNearZ(
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NEAR_DEPTH,
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(rel - 2),
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Triangle.vin[0],
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Triangle.vin[1],
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Triangle.vin[2],
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&clipped[0],
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&clipped[1],
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&clipped[2],
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&clipped[3]
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);
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/* The potential 4 new vertices that can be output by clipping the triangle. Initialized in the below branches */
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pvr_vertex_t* vout[4];
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if(tri_result == TRIANGLE_CLIP_RESULT_NO_CHANGE) {
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/* Nothing changed, we're fine */
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} else if(tri_result == TRIANGLE_CLIP_RESULT_DROP_TRIANGLE) {
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/* As we're dealing with triangle strips, we have the following situations:
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* 1. This is the first trangle. We can drop the first vertex, reverse the other two, subsequent
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* triangles will be formed from them. If there are no remaining vertices (i == count - 1) then
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* we can drop all three.
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* 2. This is the second+ triangle. We mark the second triangle vertex as the "last" vertex, then
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* push the second and third vertices again (reversed) to start the new triangle. If there are no
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* more vertices (i == count - 1) we can just drop the final vertex.
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* By first triangle, it means that rel == 2 or dst - 3 is marked as a "last" vertex.
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*/
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fprintf(stderr, "Dropping triangle\n");
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/* Is this the first triangle in the strip? */
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GLboolean first_triangle = (rel == 2) || ((vertex - 3)->flags == PVR_CMD_VERTEX_EOL);
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if(first_triangle) {
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vout[0] = vertex - 2;
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vout[1] = vertex - 1;
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vout[2] = vertex;
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if(rel == (count - 1)) {
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/* Lose all 3 vertices */
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aligned_vector_resize(list_vector, list_vector->size - 3);
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dst -= 3;
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vertex = (pvr_vertex_t*) dst;
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/* Next triangle is a new one */
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Triangle.vcount = 0;
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} else {
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vout[0] = vout[2];
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/* vout[1] = vout[1]; no-op, just here as a comment so things make a bit more sense */
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/* Rewind dst by one as we just lost a vertex */
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aligned_vector_resize(list_vector, list_vector->size - 1);
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dst--;
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vertex = (pvr_vertex_t*) dst;
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/* Two vertices are populated for the current triangle now */
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Triangle.vcount = 2;
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}
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} else {
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if(rel == (count - 1)) {
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/* This is the last vertex in the strip and we're dropping this triangle so just drop a vertex*/
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aligned_vector_resize(list_vector, list_vector->size - 1);
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dst--;
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vertex = (pvr_vertex_t*) dst;
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} else {
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/* This is a bit weird. We're dropping a triangle, but we have to add an additional vertex. This is because
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* if this triangle is in the middle of the strip, and we drop the 3rd vertex then we break the following triangle.
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* so what we do is end the triangle strip at vertex 2 of the current triangle, then re-add vertex 2 and vertex 3
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* in reverse so that the next triangle works. This might seem wasteful but actually that triangle could be subsequently
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* dropped entirely as it'll be the "first_triangle" next time around. */
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/* Make room at the end of the vector */
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aligned_vector_extend(list_vector, 1);
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/* Deal with any realloc that just happened */
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dst = aligned_vector_at(list_vector, i);
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vertex = (pvr_vertex_t*) dst;
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/* Set up the output pointers */
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vout[0] = vertex - 2;
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vout[1] = vertex - 1;
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vout[2] = vertex;
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vout[3] = vertex + 3;
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/* Mark second vertex as the end of the strip, duplicate the second vertex
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* to create the start of the next strip
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*/
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vout[1]->flags = PVR_CMD_VERTEX_EOL;
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*vout[3] = *Triangle.vin[1];
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dst = (PVRCommand*) vout[3];
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vertex = vout[3];
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/* Current triangle has two vertices */
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Triangle.vcount = 2;
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}
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}
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} else if(tri_result == TRIANGLE_CLIP_RESULT_ALTERED_VERTICES) {
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} else if(tri_result == TRIANGLE_CLIP_RESULT_ALTERED_AND_CREATED_VERTEX) {
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}
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/* Reset for the next triangle */
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Triangle.vout[0] = Triangle.vout[1];
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Triangle.vout[1] = Triangle.vout[2];
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Triangle.vin[0] = Triangle.vin[1];
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Triangle.vin[1] = Triangle.vin[2];
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Triangle.w[0] = Triangle.w[1];
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Triangle.w[1] = Triangle.w[2];
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Triangle.vcount = 2;
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@ -360,7 +464,7 @@ static void submitVertices(GLenum mode, GLsizei first, GLsizei count, GLenum typ
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++dst;
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}
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pvr_vertex_t* v = (pvr_vertex_t*) aligned_vector_at(&activePolyList()->vector, start_of_output);
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pvr_vertex_t* v = (pvr_vertex_t*) aligned_vector_at(list_vector, start_of_output);
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/* Loop 2: Perspective division */
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for(rel = 0, i = start_of_output; i < activePolyList()->vector.size; ++rel, ++i) {
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