doylet/DTRenderer
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Improve triangle rasteriser

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Doyle Thai 2017-05-11 17:28:27 +10:00
parent d9ce1e1079
commit bdb4b89bbf
1 changed files with 169 additions and 29 deletions
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194
src/DRenderer.cpp
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@ -4,8 +4,20 @@
#define DQN_IMPLEMENTATION #define DQN_IMPLEMENTATION
#include "dqn.h" #include "dqn.h"
#include <math.h> FILE_SCOPE inline void SetPixel(PlatformRenderBuffer *const renderBuffer,
FILE_SCOPE void DR_DrawLine(PlatformRenderBuffer *const renderBuffer, DqnV2i a, const i32 x, const i32 y, DqnV3 color)
{
if (!renderBuffer) return;
if (x < 0 || x > renderBuffer->width - 1) return;
if (y < 0 || y > renderBuffer->height - 1) return;
u32 *const bitmapPtr = (u32 *)renderBuffer->memory;
const u32 pitchInU32 = (renderBuffer->width * renderBuffer->bytesPerPixel) / 4;
u32 pixel = ((i32)color.r << 16) | ((i32)color.g << 8) | ((i32)color.b << 0);
bitmapPtr[x + (y * pitchInU32)] = pixel;
}
FILE_SCOPE void DrawLine(PlatformRenderBuffer *const renderBuffer, DqnV2i a,
DqnV2i b, DqnV3 color) DqnV2i b, DqnV3 color)
{ {
if (!renderBuffer) return; if (!renderBuffer) return;
@ -50,14 +62,10 @@ FILE_SCOPE void DR_DrawLine(PlatformRenderBuffer *const renderBuffer, DqnV2i a,
plotY = &newY; plotY = &newY;
} }
const u32 pitchInU32 =
(renderBuffer->width * renderBuffer->bytesPerPixel) / 4;
u32 *const bitmapPtr = (u32 *)renderBuffer->memory;
u32 pixel = ((i32)color.r << 16) | ((i32)color.g << 8) | ((i32)color.b << 0);
for (i32 iterateX = 0; iterateX < numIterations; iterateX++) for (i32 iterateX = 0; iterateX < numIterations; iterateX++)
{ {
newX = a.x + iterateX; newX = a.x + iterateX;
bitmapPtr[*plotX + (*plotY * pitchInU32)] = pixel; SetPixel(renderBuffer, *plotX, *plotY, color);
distAccumulator += distFromPixelOrigin; distAccumulator += distFromPixelOrigin;
if (distAccumulator > run) if (distAccumulator > run)
@ -68,26 +76,140 @@ FILE_SCOPE void DR_DrawLine(PlatformRenderBuffer *const renderBuffer, DqnV2i a,
} }
} }
FILE_SCOPE void DR_DrawTriangle(PlatformRenderBuffer *const renderBuffer, FILE_SCOPE void DrawTriangle(PlatformRenderBuffer *const renderBuffer,
DqnV2 p1, DqnV2 p2, DqnV2 p3, DqnV3 color) const DqnV2 p1, const DqnV2 p2, const DqnV2 p3,
const DqnV3 color)
{ {
DR_DrawLine(renderBuffer, p1, p2, color); DqnV2i max = DqnV2i_2f(DQN_MAX(DQN_MAX(p1.x, p2.x), p3.x),
DR_DrawLine(renderBuffer, p2, p3, color); DQN_MAX(DQN_MAX(p1.y, p2.y), p3.y));
DR_DrawLine(renderBuffer, p3, p1, color); DqnV2i min = DqnV2i_2f(DQN_MIN(DQN_MIN(p1.x, p2.x), p3.x),
DQN_MIN(DQN_MIN(p1.y, p2.y), p3.y));
// NOTE(doyle): This is just an desc sort using bubble sort on 3 elements min.x = DQN_MAX(min.x, 0);
if (p1.y < p2.y) DQN_SWAP(DqnV2i, p1, p2); min.y = DQN_MAX(min.y, 0);
if (p2.y < p3.y) DQN_SWAP(DqnV2i, p1, p3);
if (p1.y < p2.y) DQN_SWAP(DqnV2i, p2, p3);
i32 y1i = (i32)(p1.y + 0.5f); max.x = DQN_MIN(max.x, renderBuffer->width - 1);
i32 y2i = (i32)(p2.y + 0.5f); max.y = DQN_MIN(max.y, renderBuffer->height - 1);
i32 y3i = (i32)(p3.y + 0.5f);
if (y1i == y3i) return; // Zero height triangle DrawLine(renderBuffer, DqnV2i_2i(min.x, min.y), DqnV2i_2i(min.x, max.y), color);
DrawLine(renderBuffer, DqnV2i_2i(min.x, max.y), DqnV2i_2i(max.x, max.y), color);
DrawLine(renderBuffer, DqnV2i_2i(max.x, max.y), DqnV2i_2i(max.x, min.y), color);
DrawLine(renderBuffer, DqnV2i_2i(max.x, min.y), DqnV2i_2i(min.x, min.y), color);
DqnV2 a = p1;
DqnV2 b = p2;
DqnV2 c = p3;
f32 area2Times = ((b.x - a.x) * (b.y + a.y)) + ((c.x - b.x) * (c.y + b.y)) +
((a.x - c.x) * (a.y + c.y));
if (area2Times < 0)
{
// Counter-clockwise, do nothing this is what we want.
}
else
{
// Clockwise swap any point to make it clockwise
DQN_SWAP(DqnV2, b, c);
} }
FILE_SCOPE void DR_ClearRenderBuffer(PlatformRenderBuffer *const renderBuffer, DqnV3 color) /*
NOTE(doyle): Given two points that form a line and an extra point
to test, we can determine whether a point lies on the line, or is
to the left or right of a the line.
First forming a 3x3 matrix of our terms and deriving a 2x2 matrix
by subtracting the 1st column from the 2nd and 1st column from
the third.
| ax bx cx | | (bx - ax) (cx - ax) |
m = | ay by cy | ==> | (by - ay) (cy - ay) |
| 1 1 1 |
From our 2x2 representation we can calculate the determinant
which gives us the signed area of the triangle extended into
a parallelogram.
det(m) = (bx - ax)(cy - ay) - (by - ay)(cx - ax)
Depending on the order of the vertices supplied, if it's
- CCW and c(x,y) is outside the triangle, the signed area is negative
- CCW and c(x,y) is inside the triangle, the signed area is positive
- CW and c(x,y) is outside the triangle, the signed area is positive
- CW and c(x,y) is inside the triangle, the signed area is negative
NOTE(doyle): The det(m) can be rearranged if expanded to be
SignedArea(cx, cy) = (ay - by)cx + (bx - ay)cy + (ax*by + ay*bx)
When we scan to fill our triangle we go pixel by pixel, left to right,
bottom to top, notice that this translates to +1 for x and +1 for y, i.e.
The first pixel's signed area is cx, then cx+1, cx+2 .. etc
SignedArea(cx, cy) = (ay - by)cx + (bx - ax)cy + (ax*by + ay*bx)
SignedArea(cx+1, cy) = (ay - by)cx+1 + (bx - ax)cy + (ax*by + ay*bx)
Then
SignedArea(cx+1, cy) - SignedArea(cx, cy) =
(ay - by)cx+1 + (bx - ax)cy + (ax*by + ay*bx)
- (ay - by)cx + (bx - ax)cy + (ax*by + ay*bx)
= (ay - by)cx+1 - (ay - by)cx
= (ay - by)(cx+1 - cx)
= (ay - by)(1) = (ay - by)
Similarly when progressing in y
SignedArea(cx, cy) = (ay - by)cx + (bx - ay)cy + (ax*by + ay*bx)
SignedArea(cx, cy+1) = (ay - by)cx + (bx - ay)cy+1 + (ax*by + ay*bx)
Then
SignedArea(cx, cy+1) - SignedArea(cx, cy) =
(ay - by)cx + (bx - ax)cy+1 + (ax*by + ay*bx)
- (ay - by)cx + (bx - ax)cy + (ax*by + ay*bx)
= (bx - ax)cy+1 - (bx - ax)cy
= (bx - ax)(cy+1 - cy)
= (bx - ax)(1) = (bx - ax)
Then we can see that when we progress along x, we only need to change by
the value of SignedArea by (ay - by) and similarly for y, (bx - ay)
*/
DqnV2i scanP = DqnV2i_2i(min.x, min.y);
f32 signedArea1 = ((b.x - a.x) * (scanP.y - a.y)) - ((b.y - a.y) * (scanP.x - a.x));
f32 signedArea1DeltaX = a.y - b.y;
f32 signedArea1DeltaY = b.x - a.x;
f32 signedArea2 = ((c.x - b.x) * (scanP.y - b.y)) - ((c.y - b.y) * (scanP.x - b.x));
f32 signedArea2DeltaX = b.y - c.y;
f32 signedArea2DeltaY = c.x - b.x;
f32 signedArea3 = ((a.x - c.x) * (scanP.y - c.y)) - ((a.y - c.y) * (scanP.x - c.x));
f32 signedArea3DeltaX = c.y - a.y;
f32 signedArea3DeltaY = a.x - c.x;
for (scanP.y = min.y; scanP.y < max.y; scanP.y++)
{
f32 signedArea1Row = signedArea1;
f32 signedArea2Row = signedArea2;
f32 signedArea3Row = signedArea3;
for (scanP.x = min.x; scanP.x < max.x; scanP.x++)
{
if (signedArea1Row >= 0 && signedArea2Row >= 0 && signedArea3Row >= 0)
{
SetPixel(renderBuffer, scanP.x, scanP.y, color);
}
signedArea1Row += signedArea1DeltaX;
signedArea2Row += signedArea2DeltaX;
signedArea3Row += signedArea3DeltaX;
}
signedArea1 += signedArea1DeltaY;
signedArea2 += signedArea2DeltaY;
signedArea3 += signedArea3DeltaY;
}
}
FILE_SCOPE void ClearRenderBuffer(PlatformRenderBuffer *const renderBuffer, DqnV3 color)
{ {
if (!renderBuffer) return; if (!renderBuffer) return;
@ -111,7 +233,7 @@ extern "C" void DR_Update(PlatformRenderBuffer *const renderBuffer,
PlatformInput *const input, PlatformInput *const input,
PlatformMemory *const memory) PlatformMemory *const memory)
{ {
DR_ClearRenderBuffer(renderBuffer, DqnV3_3f(0, 0, 0)); ClearRenderBuffer(renderBuffer, DqnV3_3f(0, 0, 0));
DqnV3 colorRed = DqnV3_3i(255, 0, 0); DqnV3 colorRed = DqnV3_3i(255, 0, 0);
DqnV2i bufferMidP = DqnV2i_2f(renderBuffer->width * 0.5f, renderBuffer->height * 0.5f); DqnV2i bufferMidP = DqnV2i_2f(renderBuffer->width * 0.5f, renderBuffer->height * 0.5f);
@ -120,13 +242,31 @@ extern "C" void DR_Update(PlatformRenderBuffer *const renderBuffer,
DqnV2 t0[3] = {DqnV2_2i(10, 70), DqnV2_2i(50, 160), DqnV2_2i(70, 80)}; DqnV2 t0[3] = {DqnV2_2i(10, 70), DqnV2_2i(50, 160), DqnV2_2i(70, 80)};
DqnV2 t1[3] = {DqnV2_2i(180, 50), DqnV2_2i(150, 1), DqnV2_2i(70, 180)}; DqnV2 t1[3] = {DqnV2_2i(180, 50), DqnV2_2i(150, 1), DqnV2_2i(70, 180)};
DqnV2 t2[3] = {DqnV2_2i(180, 150), DqnV2_2i(120, 160), DqnV2_2i(130, 180)}; DqnV2 t2[3] = {DqnV2_2i(180, 150), DqnV2_2i(120, 160), DqnV2_2i(130, 180)};
DqnV2 t3[3] = { LOCAL_PERSIST DqnV2 t3[3] = {
DqnV2_2i(boundsOffset, boundsOffset), DqnV2_2i(boundsOffset, boundsOffset),
DqnV2_2i(bufferMidP.w, renderBuffer->height - boundsOffset), DqnV2_2i(bufferMidP.w, renderBuffer->height - boundsOffset),
DqnV2_2i(renderBuffer->width - boundsOffset, boundsOffset)}; DqnV2_2i(renderBuffer->width - boundsOffset, boundsOffset)};
DR_DrawTriangle(renderBuffer, t0[0], t0[1], t0[2], colorRed); f32 minX = (f32)(renderBuffer->width - 1);
// DR_DrawTriangle(renderBuffer, t1[0], t1[1], t1[2], colorRed); f32 maxX = 0;
// DR_DrawTriangle(renderBuffer, t2[0], t2[1], t2[2], colorRed); for (i32 i = 0; i < DQN_ARRAY_COUNT(t3); i++)
// DR_DrawTriangle(renderBuffer, t3[0], t3[1], t3[2], colorRed); {
t3[i].x += input->deltaForFrame * 2.0f;
minX = DQN_MIN(t3[i].x, minX);
maxX = DQN_MAX(t3[i].x, maxX);
}
if (minX >= renderBuffer->width - 1)
{
f32 triangleWidth = maxX - minX;
for (i32 i = 0; i < DQN_ARRAY_COUNT(t3); i++)
{
t3[i].x -= (minX + triangleWidth);
}
}
DrawTriangle(renderBuffer, t0[0], t0[1], t0[2], colorRed);
DrawTriangle(renderBuffer, t1[0], t1[1], t1[2], colorRed);
DrawTriangle(renderBuffer, t2[0], t2[1], t2[2], colorRed);
DrawTriangle(renderBuffer, t3[0], t3[1], t3[2], colorRed);
} }