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[rshapes] Add DrawTriangleLinesEx()

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Add DrawTriangleLinesEx() to the API for consistency with other shape drawing functions.
This commit is contained in:
Matthew Roush 2026-07-20 03:10:59 -04:00
commit 0c56ca6633
2 changed files with 161 additions and 0 deletions
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1
src/raylib.h
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@ -1284,6 +1284,7 @@ RLAPI void DrawLineDashed(Vector2 startPos, Vector2 endPos, int dashSize, int sp
RLAPI void DrawTriangle(Vector2 v1, Vector2 v2, Vector2 v3, Color color); // Draw a color-filled triangle, counter-clockwise vertex order
RLAPI void DrawTriangleGradient(Vector2 v1, Vector2 v2, Vector2 v3, Color c1, Color c2, Color c3); // Draw triangle with interpolated colors, counter-clockwise vertex/color order
RLAPI void DrawTriangleLines(Vector2 v1, Vector2 v2, Vector2 v3, Color color); // Draw triangle outline, counter-clockwise vertex order
RLAPI void DrawTriangleLinesEx(Vector2 v1, Vector2 v2, Vector2 v3, float thick, Color color); // Draw triangle outline with line thickness, counter-clockwise vertex order
RLAPI void DrawTriangleFan(const Vector2 *points, int pointCount, Color color); // Draw a triangle fan defined by points (first vertex is the center)
RLAPI void DrawTriangleStrip(const Vector2 *points, int pointCount, Color color); // Draw a triangle strip defined by points
RLAPI void DrawRectangle(int posX, int posY, int width, int height, Color color); // Draw a color-filled rectangle

160
src/rshapes.c
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@ -375,6 +375,166 @@ void DrawTriangleLines(Vector2 v1, Vector2 v2, Vector2 v3, Color color)
rlEnd();
}
// Draw a triangle using lines with thickness
// NOTE: Vertex must be provided in counter-clockwise order
void DrawTriangleLinesEx(Vector2 v1, Vector2 v2, Vector2 v3, float thick, Color color)
{
/*
A sketch to make things simpler
The exterior points are v1-3, the interior points are v4-6, and the exterior edges are e1-3
v1
/\
/v4\
// \\
// \\
e3 // \\ e2
// \\
// \\
//v5 v6\\
v2==============v3
e1
*/
Vector2 e1 = {v2.x - v3.x, v2.y - v3.y};
Vector2 e2 = {v3.x - v1.x, v3.y - v1.y};
Vector2 e3 = {v1.x - v2.x, v1.y - v2.y};
float e1Length = sqrtf(e1.x*e1.x + e1.y*e1.y);
float e2Length = sqrtf(e2.x*e2.x + e2.y*e2.y);
float e3Length = sqrtf(e3.x*e3.x + e3.y*e3.y);
float perimeter = e1Length + e2Length + e3Length;
float semiperimeter = perimeter/2.0f;
// The incenter of a triangle is equidistant from each edge, which is useful for drawing a nice looking outline
Vector2 incenter = {
(e1Length*v1.x + e2Length*v2.x + e3Length*v3.x)/perimeter,
(e1Length*v1.y + e2Length*v2.y + e3Length*v3.y)/perimeter
};
// The inradius of a triangle is the radius of the biggest circle that can fit inside of said triangle
// That circle is also centered on the incenter
float inradius = sqrtf(((semiperimeter - e1Length)*(semiperimeter - e2Length)*(semiperimeter - e3Length))/semiperimeter);
// The triangle (v1, v2, v3) will be scaled by this to get (v4, v5, v6)
float scale = 1.0f - thick/inradius;
// Just a filled-in triangle
if (scale <= 0.0f)
{
DrawTriangle(v1, v2, v3, color);
return;
}
// In order for the scaling to be correct, the incenter has to be at the origin (0, 0) when scaling
Vector2 v4 = {incenter.x + (v1.x - incenter.x)*scale, incenter.y + (v1.y - incenter.y)*scale};
Vector2 v5 = {incenter.x + (v2.x - incenter.x)*scale, incenter.y + (v2.y - incenter.y)*scale};
Vector2 v6 = {incenter.x + (v3.x - incenter.x)*scale, incenter.y + (v3.y - incenter.y)*scale};
// Swap the vertices so the winding order is correct
if (thick < 0.0f)
{
Vector2 temp = v1;
v1 = v4;
v4 = temp;
temp = v2;
v2 = v5;
v5 = temp;
temp = v3;
v3 = v6;
v6 = temp;
}
#if SUPPORT_QUADS_DRAW_MODE
rlSetTexture(GetShapesTexture().id);
Rectangle shapeRect = GetShapesTextureRectangle();
rlBegin(RL_QUADS);
rlColor4ub(color.r, color.g, color.b, color.a);
// Edge 3
rlTexCoord2f(shapeRect.x/texShapes.width, shapeRect.y/texShapes.height);
rlVertex2f(v1.x, v1.y);
rlTexCoord2f(shapeRect.x/texShapes.width, (shapeRect.y + shapeRect.height)/texShapes.height);
rlVertex2f(v2.x, v2.y);
rlTexCoord2f((shapeRect.x + shapeRect.width)/texShapes.width, (shapeRect.y + shapeRect.height)/texShapes.height);
rlVertex2f(v5.x, v5.y);
rlTexCoord2f((shapeRect.x + shapeRect.width)/texShapes.width, shapeRect.y/texShapes.height);
rlVertex2f(v4.x, v4.y);
// Edge 1
rlTexCoord2f(shapeRect.x/texShapes.width, shapeRect.y/texShapes.height);
rlVertex2f(v2.x, v2.y);
rlTexCoord2f(shapeRect.x/texShapes.width, (shapeRect.y + shapeRect.height)/texShapes.height);
rlVertex2f(v3.x, v3.y);
rlTexCoord2f((shapeRect.x + shapeRect.width)/texShapes.width, (shapeRect.y + shapeRect.height)/texShapes.height);
rlVertex2f(v6.x, v6.y);
rlTexCoord2f((shapeRect.x + shapeRect.width)/texShapes.width, shapeRect.y/texShapes.height);
rlVertex2f(v5.x, v5.y);
// Edge 2
rlTexCoord2f(shapeRect.x/texShapes.width, shapeRect.y/texShapes.height);
rlVertex2f(v3.x, v3.y);
rlTexCoord2f(shapeRect.x/texShapes.width, (shapeRect.y + shapeRect.height)/texShapes.height);
rlVertex2f(v1.x, v1.y);
rlTexCoord2f((shapeRect.x + shapeRect.width)/texShapes.width, (shapeRect.y + shapeRect.height)/texShapes.height);
rlVertex2f(v4.x, v4.y);
rlTexCoord2f((shapeRect.x + shapeRect.width)/texShapes.width, shapeRect.y/texShapes.height);
rlVertex2f(v6.x, v6.y);
rlEnd();
rlSetTexture(0);
#else
rlBegin(RL_TRIANGLES);
rlColor4ub(color.r, color.g, color.b, color.a);
// Edge 3
rlVertex2f(v1.x, v1.y);
rlVertex2f(v2.x, v2.y);
rlVertex2f(v4.x, v4.y);
rlVertex2f(v2.x, v2.y);
rlVertex2f(v5.x, v5.y);
rlVertex2f(v4.x, v4.y);
// Edge 1
rlVertex2f(v2.x, v2.y);
rlVertex2f(v3.x, v3.y);
rlVertex2f(v5.x, v5.y);
rlVertex2f(v3.x, v3.y);
rlVertex2f(v6.x, v6.y);
rlVertex2f(v5.x, v5.y);
// Edge 2
rlVertex2f(v3.x, v3.y);
rlVertex2f(v1.x, v1.y);
rlVertex2f(v4.x, v4.y);
rlVertex2f(v3.x, v3.y);
rlVertex2f(v4.x, v4.y);
rlVertex2f(v6.x, v6.y);
rlEnd();
#endif
}
// Draw a triangle fan defined by points
// NOTE: First vertex provided is the center, shared by all triangles
// By default, following vertex should be provided in counter-clockwise order