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Add alpha blending and alpha for primitives

This commit is contained in:
Doyle Thai 2017-05-12 18:20:59 +10:00
parent afcd158d7d
commit 872ee9efa4
2 changed files with 97 additions and 44 deletions
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135
src/DRenderer.cpp
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@ -33,23 +33,65 @@ typedef struct DRState
DRFont font;
} DRState;
FILE_SCOPE inline void SetPixel(PlatformRenderBuffer *const renderBuffer,
const i32 x, const i32 y, DqnV3 color)
FILE_SCOPE inline DqnV4 PreMultiplyAlpha(DqnV4 color)
{
DqnV4 result;
f32 normA = color.a / 255.0f;
result.r = color.r * normA;
result.g = color.g * normA;
result.b = color.b * normA;
result.a = color.a;
return result;
}
// IMPORTANT(doyle): Color is expected to be premultiplied already
FILE_SCOPE inline void SetPixel(PlatformRenderBuffer *const renderBuffer,
const i32 x, const i32 y, const DqnV4 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);
f32 newA = color.a;
f32 newANorm = newA / 255.0f;
f32 newR = color.r;
f32 newG = color.g;
f32 newB = color.b;
u32 src = bitmapPtr[x + (y * pitchInU32)];
f32 srcR = (f32)((src >> 16) & 0xFF);
f32 srcG = (f32)((src >> 8) & 0xFF);
f32 srcB = (f32)((src >> 0) & 0xFF);
// NOTE(doyle): AlphaBlend equations is (alpha * new) + (1 - alpha) * src.
// IMPORTANT(doyle): We pre-multiply so we can take out the (alpha * new)
f32 invANorm = 1 - newANorm;
// f32 destA = (((1 - srcA) * newA) + srcA) * 255.0f;
f32 destR = newR + (invANorm * srcR);
f32 destG = newG + (invANorm * srcG);
f32 destB = newB + (invANorm * srcB);
// DQN_ASSERT(destA >= 0 && destA <= 255.0f);
DQN_ASSERT(destR >= 0 && destR <= 255.0f);
DQN_ASSERT(destG >= 0 && destG <= 255.0f);
DQN_ASSERT(destB >= 0 && destB <= 255.0f);
u32 pixel = ((u32)(destR) << 16 |
(u32)(destG) << 8 |
(u32)(destB) << 0);
bitmapPtr[x + (y * pitchInU32)] = pixel;
}
FILE_SCOPE void DrawLine(PlatformRenderBuffer *const renderBuffer, DqnV2i a,
DqnV2i b, DqnV3 color)
DqnV2i b, DqnV4 color)
{
if (!renderBuffer) return;
color = PreMultiplyAlpha(color);
bool yTallerThanX = false;
if (DQN_ABS(a.x - b.x) < DQN_ABS(a.y - b.y))
@ -107,9 +149,10 @@ FILE_SCOPE void DrawLine(PlatformRenderBuffer *const renderBuffer, DqnV2i a,
FILE_SCOPE void DrawTriangle(PlatformRenderBuffer *const renderBuffer,
const DqnV2 p1, const DqnV2 p2, const DqnV2 p3,
const DqnV3 color)
DqnV4 color)
{
__rdtsc();
color = PreMultiplyAlpha(color);
DqnV2i max = DqnV2i_2f(DQN_MAX(DQN_MAX(p1.x, p2.x), p3.x),
DQN_MAX(DQN_MAX(p1.y, p2.y), p3.y));
DqnV2i min = DqnV2i_2f(DQN_MIN(DQN_MIN(p1.x, p2.x), p3.x),
@ -150,8 +193,15 @@ FILE_SCOPE void DrawTriangle(PlatformRenderBuffer *const renderBuffer,
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.
Then you can imagine if we iterate over the triangle vertexes, 2 at at
time and a last point P, being the point we want to test if it's inside
the triangle, then if the point is considered to lie on the side of the
line forming the interior of the triangle for all 3 vertexes then the
point is inside the triangle. We can do this using the determinant.
First forming a 3x3 matrix of our terms with a, b being from the triangle
and test point c, we can derive 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) |
@ -163,10 +213,10 @@ FILE_SCOPE void DrawTriangle(PlatformRenderBuffer *const renderBuffer,
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
- CCW and c(x,y) is outside the line (triangle), the signed area is negative
- CCW and c(x,y) is inside the line (triangle), the signed area is positive
- CW and c(x,y) is outside the line (triangle), the signed area is positive
- CW and c(x,y) is inside the line (triangle), the signed area is negative
/////////////////////////////////////////////////////////////////////////
// Optimising the Determinant Calculation
@ -236,9 +286,9 @@ FILE_SCOPE void DrawTriangle(PlatformRenderBuffer *const renderBuffer,
This is normalised to the area's sum, but we can trivially turn this into
a normalised version by dividing the area of the parallelogram, i.e.
BaryCentricA(P) = (SignedArea(P) w. vertex C and B)/SignedArea(of the orig triangle)
BaryCentricB(P) = (SignedArea(P) w. vertex A and C)/SignedArea(of the orig triangle)
BaryCentricC(P) = (SignedArea(P) w. vertex A and B)/SignedArea(of the orig triangle)
BaryCentricC(P) = (SignedArea(P) with vertex A and B)/SignedArea(with the orig triangle vertex)
BaryCentricA(P) = (SignedArea(P) with vertex B and C)/SignedArea(with the orig triangle vertex)
BaryCentricB(P) = (SignedArea(P) with vertex C and A)/SignedArea(with the orig triangle vertex)
*/
DqnV2i scanP = DqnV2i_2i(min.x, min.y);
@ -254,6 +304,8 @@ FILE_SCOPE void DrawTriangle(PlatformRenderBuffer *const renderBuffer,
f32 signedArea3DeltaX = c.y - a.y;
f32 signedArea3DeltaY = a.x - c.x;
f32 invSignedAreaParallelogram = 1 / ((b.x - a.x) * (c.y - a.y) - (b.y - a.y) * (c.x - a.x));
for (scanP.y = min.y; scanP.y < max.y; scanP.y++)
{
@ -281,12 +333,13 @@ FILE_SCOPE void DrawTriangle(PlatformRenderBuffer *const renderBuffer,
FILE_SCOPE void DrawText(PlatformRenderBuffer *const renderBuffer,
const DRFont font, DqnV2 pos, const char *const text,
i32 len = -1)
DqnV4 color = DqnV4_4f(255, 255, 255, 255), i32 len = -1)
{
if (!text) return;
if (len == -1) len = Dqn_strlen(text);
i32 index = 0;
color = PreMultiplyAlpha(color);
while (index < len)
{
if (text[index] < font.codepointRange.min &&
@ -334,30 +387,20 @@ FILE_SCOPE void DrawText(PlatformRenderBuffer *const renderBuffer,
{
for (i32 x = 0; x < fontWidth; x++)
{
i32 yOffset = fontHeight - y;
u8 fontPixel = fontPtr[x + (yOffset * fontPitch)];
if (fontPixel == 0) continue;
i32 yOffset = fontHeight - y;
u8 srcA = fontPtr[x + (yOffset * fontPitch)];
if (srcA == 0) continue;
f32 srcA = (fontPixel / 255.0f);
f32 srcR = (fontPixel / 255.0f);
f32 srcG = (fontPixel / 255.0f);
f32 srcB = (fontPixel / 255.0f);
f32 srcANorm = srcA / 255.0f;
DqnV4 resultColor = {};
resultColor.r = color.r * srcANorm;
resultColor.g = color.g * srcANorm;
resultColor.b = color.b * srcANorm;
resultColor.a = color.a * srcANorm;
u32 offset = x + (y * renderBuffer->width);
u32 old = screenPtr[offset];
f32 oldR = (f32)((old >> 16) & 0xFF) / 255.0f;
f32 oldG = (f32)((old >> 8) & 0xFF) / 255.0f;
f32 oldB = (f32)((old >> 0) & 0xFF) / 255.0f;
f32 invA = 1 - srcA;
f32 destR = srcR + (invA * oldR);
f32 destG = srcG + (invA * oldG);
f32 destB = srcB + (invA * oldB);
u32 dest = ((u32)(destR * 255.0f) << 16) |
((u32)(destG * 255.0f) << 8) |
((u32)(destB * 255.0f) << 0);
screenPtr[offset] = dest;
i32 actualX = (i32)(screenRect.min.x + x);
i32 actualY = (i32)(screenRect.min.y + y - fontHeightOffset);
SetPixel(renderBuffer, actualX, actualY, resultColor);
}
}
}
@ -451,6 +494,7 @@ FILE_SCOPE void BitmapFontCreate(const PlatformAPI api,
f32 alpha = (f32)(font->bitmap[index]) / 255.0f;
f32 color = alpha;
f32 preMulAlphaColor = color * alpha;
DQN_ASSERT(preMulAlphaColor >= 0.0f && preMulAlphaColor <= 255.0f);
font->bitmap[index] = (u8)(preMulAlphaColor * 255.0f);
}
@ -480,8 +524,8 @@ extern "C" void DR_Update(PlatformRenderBuffer *const renderBuffer,
DqnV2i_2i(256, 256), DqnV2i_2i(' ', '~'), 35);
}
ClearRenderBuffer(renderBuffer, DqnV3_3f(0, 0, 0));
DqnV3 colorRed = DqnV3_3i(255, 0, 0);
ClearRenderBuffer(renderBuffer, DqnV3_3f(0, 255, 0));
DqnV4 colorRed = DqnV4_4i(50, 0, 0, 255);
DqnV2i bufferMidP = DqnV2i_2f(renderBuffer->width * 0.5f, renderBuffer->height * 0.5f);
i32 boundsOffset = 50;
@ -497,7 +541,7 @@ extern "C" void DR_Update(PlatformRenderBuffer *const renderBuffer,
f32 maxX = 0;
for (i32 i = 0; i < DQN_ARRAY_COUNT(t3); i++)
{
t3[i].x += input->deltaForFrame * 2.0f;
// t3[i].x += input->deltaForFrame * 2.0f;
minX = DQN_MIN(t3[i].x, minX);
maxX = DQN_MAX(t3[i].x, maxX);
}
@ -511,11 +555,14 @@ extern "C" void DR_Update(PlatformRenderBuffer *const renderBuffer,
}
}
DqnV2 fontP = DqnV2_2i(200, 180);
DrawText(renderBuffer, state->font, fontP, "hello world!");
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);
DqnV2 fontP = DqnV2_2i(200, 180);
DrawText(renderBuffer, state->font, fontP, "hello world!");
DqnV4 colorRedHalfA = DqnV4_4i(255, 0, 0, 190);
DrawTriangle(renderBuffer, t3[0], t3[1], t3[2], colorRedHalfA);
}

6
src/Win32DRenderer.cpp
View File

@ -110,6 +110,7 @@ FILE_SCOPE void Win32DisplayRenderBitmap(Win32RenderBitmap renderBitmap,
HDC deviceContext, LONG width,
LONG height)
{
#if 0
HDC stretchDC = CreateCompatibleDC(deviceContext);
SelectObject(stretchDC, renderBitmap.handle);
// DQN_ASSERT(renderBitmap.width == width);
@ -117,6 +118,11 @@ FILE_SCOPE void Win32DisplayRenderBitmap(Win32RenderBitmap renderBitmap,
StretchBlt(deviceContext, 0, 0, width, height, stretchDC, 0, 0,
renderBitmap.width, renderBitmap.height, SRCCOPY);
DeleteDC(stretchDC);
#else
StretchDIBits(deviceContext, 0, 0, width, height, 0, 0, renderBitmap.width,
renderBitmap.height, renderBitmap.memory,
&renderBitmap.info, DIB_RGB_COLORS, SRCCOPY);
#endif
}
FILETIME Win32GetLastWriteTime(const char *const srcName)