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Fix degenerate tris showing up in certain configs 

Occasionally with the right orientation, degenerate triangles will appear as
they are no longer zero-area triangles which OGL can cull during rendering. The
issue comes from having to manually ensure each primitive in the rendering
pipeline sent to the render groups were correctly marked with degenerate
vertexes.

Instead, we can now just pass the vertex points straight through, using
a begin() and end() structure which will append the start and ending degenerate
vertexes for us.
This commit is contained in:
Doyle Thai 2016-11-17 21:03:55 +11:00
parent 064d17d34c
commit 17dc6cc6fc
3 changed files with 114 additions and 73 deletions
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3
src/Asteroid.c
View File

@ -53,6 +53,7 @@ void initRenderer(GameState *state, v2 windowSize) {
// NOTE(doyle): Value to map a screen coordinate to NDC coordinate
renderer->vertexNdcFactor =
V2(1.0f / renderer->size.w, 1.0f / renderer->size.h);
renderer->groupIndexForVertexBatch = -1;
const mat4 projection =
mat4_ortho(0.0f, renderer->size.w, 0.0f, renderer->size.h, 0.0f, 1.0f);
@ -568,6 +569,7 @@ void asteroid_gameUpdateAndRender(GameState *state, Memory *memory,
V4(1.0f, 0, 0, 1.0f), flags);
}
#if 1
TrianglePoints triangle = {0};
triangle.points[0] = V2(100, 200);
triangle.points[1] = V2(200, 100);
@ -582,6 +584,7 @@ void asteroid_gameUpdateAndRender(GameState *state, Memory *memory,
debug_drawUi(state, dt);
debug_clearCounter();
#endif
renderer_renderGroups(&state->renderer);
}

175
src/Renderer.c
View File

@ -18,15 +18,68 @@ typedef struct RenderTriangle
Vertex vertex[3];
} RenderTriangle_;
INTERNAL void addVertexToRenderGroup(Renderer *renderer, Texture *tex, v4 color,
Vertex *vertexList, i32 numVertexes,
enum RenderMode targetRenderMode,
RenderFlags flags)
// NOTE(doyle): A vertex batch is the batch of vertexes comprised to make one
// shape
INTERNAL void beginVertexBatch(Renderer *renderer)
{
ASSERT(renderer->vertexBatchState == vertexbatchstate_off);
ASSERT(renderer->groupIndexForVertexBatch == -1);
renderer->vertexBatchState = vertexbatchstate_initial_add;
}
#ifdef DENGINE_DEBUG
/*
NOTE(doyle): Entity rendering is always done in two pairs of
triangles, i.e. quad. To batch render quads as a triangle strip, we
need to create zero-area triangles which OGL will omit from
rendering. Render groups are initialised with 1 degenerate vertex and
then the first two vertexes sent to the render group are the same to
form 1 zero-area triangle strip.
A degenerate vertex has to be copied from the last vertex in the
rendering quad, to repeat this process as more entities are
renderered.
Alternative implementation is recognising if the rendered
entity is the first in its render group, then we don't need to init
a degenerate vertex, and only at the end of its vertex list. But on
subsequent renders, we need a degenerate vertex at the front to
create the zero-area triangle strip.
The first has been chosen for simplicity of code, at the cost of
1 degenerate vertex at the start of each render group. The initial degenrate
vertexes are added in the add to vertex group and the ending degenerates at
on ending a vertex batch.
*/
INTERNAL void endVertexBatch(Renderer *renderer)
{
ASSERT(renderer->vertexBatchState != vertexbatchstate_off);
ASSERT(renderer->groupIndexForVertexBatch != -1);
i32 numDegenerateVertexes = 2;
RenderGroup *group = &renderer->groups[renderer->groupIndexForVertexBatch];
i32 freeVertexSlots = renderer->groupCapacity - group->vertexIndex;
if (numDegenerateVertexes < freeVertexSlots)
{
Vertex degenerateVertex = group->vertexList[group->vertexIndex-1];
group->vertexList[group->vertexIndex++] = degenerateVertex;
group->vertexList[group->vertexIndex++] = degenerateVertex;
}
renderer->vertexBatchState = vertexbatchstate_off;
renderer->groupIndexForVertexBatch = -1;
}
INTERNAL void addVertexToRenderGroup_(Renderer *renderer, Texture *tex,
v4 color, Vertex *vertexList,
i32 numVertexes,
enum RenderMode targetRenderMode,
RenderFlags flags)
{
ASSERT(renderer->vertexBatchState != vertexbatchstate_off);
ASSERT(numVertexes > 0);
#ifdef DENGINE_DEBUG
for (i32 i = 0; i < numVertexes; i++)
debug_countIncrement(debugcount_numVertex);
#endif
@ -72,9 +125,6 @@ INTERNAL void addVertexToRenderGroup(Renderer *renderer, Texture *tex, v4 color,
/* New group, unused so initialise it */
groupIsValid = TRUE;
// NOTE(doyle): Mark first vertex as degenerate vertex
group->vertexList[group->vertexIndex++] = vertexList[0];
group->init = TRUE;
group->tex = tex;
group->color = color;
@ -89,7 +139,15 @@ INTERNAL void addVertexToRenderGroup(Renderer *renderer, Texture *tex, v4 color,
if (groupIsValid)
{
i32 freeVertexSlots = renderer->groupCapacity - group->vertexIndex;
if (numVertexes < freeVertexSlots)
// NOTE(doyle): Two at start, two at end
i32 numDegenerateVertexes = 0;
if (renderer->vertexBatchState == vertexbatchstate_initial_add)
{
numDegenerateVertexes = 2;
}
if ((numDegenerateVertexes + numVertexes) < freeVertexSlots)
{
if (i != 0)
{
@ -106,6 +164,18 @@ INTERNAL void addVertexToRenderGroup(Renderer *renderer, Texture *tex, v4 color,
/* Valid group, add to the render group for rendering */
if (targetGroup)
{
if (renderer->vertexBatchState == vertexbatchstate_initial_add)
{
targetGroup->vertexList[targetGroup->vertexIndex++] = vertexList[0];
targetGroup->vertexList[targetGroup->vertexIndex++] = vertexList[0];
renderer->vertexBatchState = vertexbatchstate_active;
// NOTE(doyle): We swap groups to the front if it is valid, so
// target group should always be 0
ASSERT(renderer->groupIndexForVertexBatch == -1);
renderer->groupIndexForVertexBatch = 0;
}
for (i32 i = 0; i < numVertexes; i++)
{
targetGroup->vertexList[targetGroup->vertexIndex++] = vertexList[i];
@ -346,33 +416,10 @@ void renderer_rect(Renderer *const renderer, Rect camera, v2 pos, v2 size,
RenderQuad_ quad = createRenderQuad(renderer, posInCameraSpace, size,
pivotPoint, rotate, *renderTex);
/*
NOTE(doyle): Entity rendering is always done in two pairs of
triangles, i.e. quad. To batch render quads as a triangle strip, we
need to create zero-area triangles which OGL will omit from
rendering. Render groups are initialised with 1 degenerate vertex and
then the first two vertexes sent to the render group are the same to
form 1 zero-area triangle strip.
A degenerate vertex has to be copied from the last vertex in the
rendering quad, to repeat this process as more entities are
renderered.
Alternative implementation is recognising if the rendered
entity is the first in its render group, then we don't need to init
a degenerate vertex, and only at the end of its vertex list. But on
subsequent renders, we need a degenerate vertex at the front to
create the zero-area triangle strip.
The first has been chosen for simplicity of code, at the cost of
1 degenerate vertex at the start of each render group.
*/
Vertex vertexList[6] = {quad.vertex[0], quad.vertex[0], quad.vertex[1],
quad.vertex[2], quad.vertex[3], quad.vertex[3]};
addVertexToRenderGroup(renderer, renderTex->tex, color, vertexList,
ARRAY_COUNT(vertexList), rendermode_quad, flags);
beginVertexBatch(renderer);
addVertexToRenderGroup_(renderer, renderTex->tex, color, quad.vertex,
ARRAY_COUNT(quad.vertex), rendermode_quad, flags);
endVertexBatch(renderer);
}
void renderer_polygon(Renderer *const renderer, Rect camera,
@ -395,32 +442,23 @@ void renderer_polygon(Renderer *const renderer, Rect camera,
Vertex triangulationBaseVertex = {0};
triangulationBaseVertex.pos = triangulationBaseP;
addVertexToRenderGroup(renderer, renderTex->tex, color,
&triangulationBaseVertex, 1, rendermode_polygon,
flags);
RenderTriangle_ lastRenderTriForDegeneration = {0};
beginVertexBatch(renderer);
for (i32 i = 1; triangulationIndex < numTrisInTriangulation; i++)
{
ASSERT((i + 1) <= numPoints);
RenderTriangle_ tri = {0};
tri.vertex[0].pos = triangulationBaseP;
tri.vertex[1].pos = polygonPoints[i + 1];
tri.vertex[2].pos = polygonPoints[i];
addVertexToRenderGroup(renderer, renderTex->tex, color, tri.vertex,
ARRAY_COUNT(tri.vertex), rendermode_polygon,
flags);
if (triangulationIndex++ >= numTrisInTriangulation)
{
lastRenderTriForDegeneration = tri;
}
}
for (i32 i = 0; i < 3; i++)
{
addVertexToRenderGroup(renderer, renderTex->tex, color,
&lastRenderTriForDegeneration.vertex[2], 1,
rendermode_polygon, flags);
addVertexToRenderGroup_(renderer, renderTex->tex, color, tri.vertex,
ARRAY_COUNT(tri.vertex), rendermode_polygon,
flags);
triangulationIndex++;
}
endVertexBatch(renderer);
}
void renderer_triangle(Renderer *const renderer, Rect camera,
@ -440,13 +478,11 @@ void renderer_triangle(Renderer *const renderer, Rect camera,
RenderTriangle_ renderTriangle = createRenderTriangle(
renderer, triangleInCamSpace, pivotPoint, rotate, *renderTex);
// NOTE(doyle): Create degenerate vertex setup
Vertex vertexList[5] = {renderTriangle.vertex[0], renderTriangle.vertex[0],
renderTriangle.vertex[1], renderTriangle.vertex[2],
renderTriangle.vertex[2]};
addVertexToRenderGroup(renderer, renderTex->tex, color, vertexList,
ARRAY_COUNT(vertexList), rendermode_triangle, flags);
beginVertexBatch(renderer);
addVertexToRenderGroup_(
renderer, renderTex->tex, color, renderTriangle.vertex,
ARRAY_COUNT(renderTriangle.vertex), rendermode_triangle, flags);
endVertexBatch(renderer);
}
void renderer_string(Renderer *const renderer, MemoryArena_ *arena, Rect camera,
@ -499,20 +535,13 @@ void renderer_string(Renderer *const renderer, MemoryArena_ *arena, Rect camera,
RenderQuad_ quad = createRenderQuad(renderer, pos, font->maxSize,
pivotPoint, rotate, renderTex);
vertexList[vertexIndex++] = quad.vertex[0];
for (i32 i = 0; i < ARRAY_COUNT(quad.vertex); i++)
{
vertexList[vertexIndex++] = quad.vertex[i];
}
vertexList[vertexIndex++] = quad.vertex[3];
beginVertexBatch(renderer);
addVertexToRenderGroup_(renderer, tex, color, quad.vertex,
ARRAY_COUNT(quad.vertex), rendermode_quad,
flags);
endVertexBatch(renderer);
pos.x += metric.advance;
}
addVertexToRenderGroup(renderer, tex, color, vertexList,
numVertexesToAlloc, rendermode_quad, flags);
// TODO(doyle): Mem free
// PLATFORM_MEM_FREE(arena, vertexList,
// sizeof(Vertex) * numVertexesToAlloc);
}
}

9
src/include/Dengine/Renderer.h
View File

@ -61,6 +61,12 @@ typedef struct RenderGroup
} RenderGroup;
enum VertexBatchState {
vertexbatchstate_off,
vertexbatchstate_initial_add,
vertexbatchstate_active,
};
typedef struct Renderer
{
u32 shaderList[shaderlist_count];
@ -69,6 +75,9 @@ typedef struct Renderer
u32 vao[rendermode_count];
u32 vbo[rendermode_count];
enum VertexBatchState vertexBatchState;
i32 groupIndexForVertexBatch;
i32 numVertexesInVbo;
v2 vertexNdcFactor;
v2 size;