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[rtextures] Adding triangle drawing function for images (#4094)
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* adding triangle drawing function for images

* remove unnecessary check

* fix an iteration mistake
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@Bigfoot71
Bigfoot71 committed Jun 23, 2024
1 parent 7773254 commit 7e50270
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5 changes: 5 additions & 0 deletions src/raylib.h
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Original file line number Diff line number Diff line change
Expand Up @@ -1381,6 +1381,11 @@ RLAPI void ImageDrawRectangle(Image *dst, int posX, int posY, int width, int hei
RLAPI void ImageDrawRectangleV(Image *dst, Vector2 position, Vector2 size, Color color); // Draw rectangle within an image (Vector version)
RLAPI void ImageDrawRectangleRec(Image *dst, Rectangle rec, Color color); // Draw rectangle within an image
RLAPI void ImageDrawRectangleLines(Image *dst, Rectangle rec, int thick, Color color); // Draw rectangle lines within an image
RLAPI void ImageDrawTriangle(Image *dst, Vector2 v1, Vector2 v2, Vector2 v3, Color color); // Draw triangle within an image
RLAPI void ImageDrawTriangleEx(Image *dst, Vector2 v1, Vector2 v2, Vector2 v3, Color c1, Color c2, Color c3); // Draw triangle with interpolated colors within an image
RLAPI void ImageDrawTriangleLines(Image *dst, Vector2 v1, Vector2 v2, Vector2 v3, Color color); // Draw triangle outline within an image
RLAPI void ImageDrawTriangleFan(Image *dst, Vector2 *points, int pointCount, Color color); // Draw a triangle fan defined by points within an image (first vertex is the center)
RLAPI void ImageDrawTriangleStrip(Image *dst, Vector2 *points, int pointCount, Color color); // Draw a triangle strip defined by points within an image
RLAPI void ImageDraw(Image *dst, Image src, Rectangle srcRec, Rectangle dstRec, Color tint); // Draw a source image within a destination image (tint applied to source)
RLAPI void ImageDrawText(Image *dst, const char *text, int posX, int posY, int fontSize, Color color); // Draw text (using default font) within an image (destination)
RLAPI void ImageDrawTextEx(Image *dst, Font font, const char *text, Vector2 position, float fontSize, float spacing, Color tint); // Draw text (custom sprite font) within an image (destination)
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188 changes: 188 additions & 0 deletions src/rtextures.c
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Expand Up @@ -3627,6 +3627,194 @@ void ImageDrawRectangleLines(Image *dst, Rectangle rec, int thick, Color color)
ImageDrawRectangle(dst, (int)rec.x, (int)(rec.y + rec.height - thick), (int)rec.width, thick, color);
}

// Draw triangle within an image
void ImageDrawTriangle(Image *dst, Vector2 v1, Vector2 v2, Vector2 v3, Color color)
{
// Calculate the 2D bounding box of the triangle
// Determine the minimum and maximum x and y coordinates of the triangle vertices
int xMin = (v1.x < v2.x)? ((v1.x < v3.x)? v1.x : v3.x) : ((v2.x < v3.x)? v2.x : v3.x);
int yMin = (v1.y < v2.y)? ((v1.y < v3.y)? v1.y : v3.y) : ((v2.y < v3.y)? v2.y : v3.y);
int xMax = (v1.x > v2.x)? ((v1.x > v3.x)? v1.x : v3.x) : ((v2.x > v3.x)? v2.x : v3.x);
int yMax = (v1.y > v2.y)? ((v1.y > v3.y)? v1.y : v3.y) : ((v2.y > v3.y)? v2.y : v3.y);

// Clamp the bounding box to the image dimensions
if (xMin < 0) xMin = 0;
if (yMin < 0) yMin = 0;
if (xMax > dst->width) xMax = dst->width;
if (yMax > dst->height) yMax = dst->height;

// Check the order of the vertices to determine if it's a front or back face
// NOTE: if signedArea is equal to 0, the face is degenerate
float signedArea = (v2.x - v1.x)*(v3.y - v1.y) - (v3.x - v1.x)*(v2.y - v1.y);
bool isBackFace = (signedArea > 0);

// Barycentric interpolation setup
// Calculate the step increments for the barycentric coordinates
int w1XStep = v3.y - v2.y, w1YStep = v2.x - v3.x;
int w2XStep = v1.y - v3.y, w2YStep = v3.x - v1.x;
int w3XStep = v2.y - v1.y, w3YStep = v1.x - v2.x;

// If the triangle is a back face, invert the steps
if (isBackFace)
{
w1XStep = -w1XStep, w1YStep = -w1YStep;
w2XStep = -w2XStep, w2YStep = -w2YStep;
w3XStep = -w3XStep, w3YStep = -w3YStep;
}

// Calculate the initial barycentric coordinates for the top-left point of the bounding box
int w1Row = (xMin - v2.x)*w1XStep + w1YStep*(yMin - v2.y);
int w2Row = (xMin - v3.x)*w2XStep + w2YStep*(yMin - v3.y);
int w3Row = (xMin - v1.x)*w3XStep + w3YStep*(yMin - v1.y);

// Rasterization loop
// Iterate through each pixel in the bounding box
for (int y = yMin; y <= yMax; y++)
{
int w1 = w1Row;
int w2 = w2Row;
int w3 = w3Row;

for (int x = xMin; x <= xMax; x++)
{
// Check if the pixel is inside the triangle using barycentric coordinates
// If it is then we can draw the pixel with the given color
if ((w1 | w2 | w3) >= 0) ImageDrawPixel(dst, x, y, color);

// Increment the barycentric coordinates for the next pixel
w1 += w1XStep;
w2 += w2XStep;
w3 += w3XStep;
}

// Move to the next row in the bounding box
w1Row += w1YStep;
w2Row += w2YStep;
w3Row += w3YStep;
}
}

// Draw triangle with interpolated colors within an image
void ImageDrawTriangleEx(Image *dst, Vector2 v1, Vector2 v2, Vector2 v3, Color c1, Color c2, Color c3)
{
// Calculate the 2D bounding box of the triangle
// Determine the minimum and maximum x and y coordinates of the triangle vertices
int xMin = (v1.x < v2.x)? ((v1.x < v3.x)? v1.x : v3.x) : ((v2.x < v3.x)? v2.x : v3.x);
int yMin = (v1.y < v2.y)? ((v1.y < v3.y)? v1.y : v3.y) : ((v2.y < v3.y)? v2.y : v3.y);
int xMax = (v1.x > v2.x)? ((v1.x > v3.x)? v1.x : v3.x) : ((v2.x > v3.x)? v2.x : v3.x);
int yMax = (v1.y > v2.y)? ((v1.y > v3.y)? v1.y : v3.y) : ((v2.y > v3.y)? v2.y : v3.y);

// Clamp the bounding box to the image dimensions
if (xMin < 0) xMin = 0;
if (yMin < 0) yMin = 0;
if (xMax > dst->width) xMax = dst->width;
if (yMax > dst->height) yMax = dst->height;

// Check the order of the vertices to determine if it's a front or back face
// NOTE: if signedArea is equal to 0, the face is degenerate
float signedArea = (v2.x - v1.x)*(v3.y - v1.y) - (v3.x - v1.x)*(v2.y - v1.y);
bool isBackFace = (signedArea > 0);

// Barycentric interpolation setup
// Calculate the step increments for the barycentric coordinates
int w1XStep = v3.y - v2.y, w1YStep = v2.x - v3.x;
int w2XStep = v1.y - v3.y, w2YStep = v3.x - v1.x;
int w3XStep = v2.y - v1.y, w3YStep = v1.x - v2.x;

// If the triangle is a back face, invert the steps
if (isBackFace)
{
w1XStep = -w1XStep, w1YStep = -w1YStep;
w2XStep = -w2XStep, w2YStep = -w2YStep;
w3XStep = -w3XStep, w3YStep = -w3YStep;
}

// Calculate the initial barycentric coordinates for the top-left point of the bounding box
int w1Row = (xMin - v2.x)*w1XStep + w1YStep*(yMin - v2.y);
int w2Row = (xMin - v3.x)*w2XStep + w2YStep*(yMin - v3.y);
int w3Row = (xMin - v1.x)*w3XStep + w3YStep*(yMin - v1.y);

// Calculate the inverse of the sum of the barycentric coordinates for normalization
// NOTE 1: Here, we act as if we multiply by 255 the reciprocal, which avoids additional
// calculations in the loop. This is acceptable because we are only interpolating colors.
// NOTE 2: This sum remains constant throughout the triangle
float wInvSum = 255.0f/(w1Row + w2Row + w3Row);

// Rasterization loop
// Iterate through each pixel in the bounding box
for (int y = yMin; y <= yMax; y++)
{
int w1 = w1Row;
int w2 = w2Row;
int w3 = w3Row;

for (int x = xMin; x <= xMax; x++)
{
// Check if the pixel is inside the triangle using barycentric coordinates
if ((w1 | w2 | w3) >= 0)
{
// Compute the normalized barycentric coordinates
unsigned char aW1 = (unsigned char)((float)w1*wInvSum);
unsigned char aW2 = (unsigned char)((float)w2*wInvSum);
unsigned char aW3 = (unsigned char)((float)w3*wInvSum);

// Interpolate the color using the barycentric coordinates
Color finalColor = { 0 };
finalColor.r = (c1.r*aW1 + c2.r*aW2 + c3.r*aW3)/255;
finalColor.g = (c1.g*aW1 + c2.g*aW2 + c3.g*aW3)/255;
finalColor.b = (c1.b*aW1 + c2.b*aW2 + c3.b*aW3)/255;
finalColor.a = (c1.a*aW1 + c2.a*aW2 + c3.a*aW3)/255;

// Draw the pixel with the interpolated color
ImageDrawPixel(dst, x, y, finalColor);
}

// Increment the barycentric coordinates for the next pixel
w1 += w1XStep;
w2 += w2XStep;
w3 += w3XStep;
}

// Move to the next row in the bounding box
w1Row += w1YStep;
w2Row += w2YStep;
w3Row += w3YStep;
}
}

// Draw triangle outline within an image
void ImageDrawTriangleLines(Image *dst, Vector2 v1, Vector2 v2, Vector2 v3, Color color)
{
ImageDrawLine(dst, v1.x, v1.y, v2.x, v2.y, color);
ImageDrawLine(dst, v2.x, v2.y, v3.x, v3.y, color);
ImageDrawLine(dst, v3.x, v3.y, v1.x, v1.y, color);
}

// Draw a triangle fan defined by points within an image (first vertex is the center)
void ImageDrawTriangleFan(Image *dst, Vector2 *points, int pointCount, Color color)
{
if (pointCount >= 3)
{
for (int i = 1; i < pointCount - 1; i++)
{
ImageDrawTriangle(dst, points[0], points[i], points[i + 1], color);
}
}
}

// Draw a triangle strip defined by points within an image
void ImageDrawTriangleStrip(Image *dst, Vector2 *points, int pointCount, Color color)
{
if (pointCount >= 3)
{
for (int i = 2; i < pointCount; i++)
{
if ((i%2) == 0) ImageDrawTriangle(dst, points[i], points[i - 2], points[i - 1], color);
else ImageDrawTriangle(dst, points[i], points[i - 1], points[i - 2], color);
}
}
}

// Draw an image (source) within an image (destination)
// NOTE: Color tint is applied to source image
void ImageDraw(Image *dst, Image src, Rectangle srcRec, Rectangle dstRec, Color tint)
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