Ensure DrawSplineSegmentBezierCubicVar renders somewhat correctly

CHANGELOG

@@ -179,6 +179,19 @@ WIP: Last update with commit from 02-Nov-2024
 [rshapes] REVIEWED: `CheckCollisionCircleRec()` (#3584) by @ubkp
 [rshapes] REVIEWED: Add more detail to function comment (#4344) by @Jeffery Myers
 [rshapes] REVIEWED: Functions that draw point arrays take them as const (#4051) by @Jeffery Myers
+[rshapes] ADDED: `DrawSplineSegmentBezierCubicVar()` (#TBD) by @AmityWilder
+[rshapes] ADDED: `GetSplineVelocityLinear()` (#TBD) by @AmityWilder
+[rshapes] ADDED: `GetSplineVelocityBezierQuad()` (#TBD) by @AmityWilder
+[rshapes] ADDED: `GetSplineVelocityBezierCubic()` (#TBD) by @AmityWilder
+[rshapes] ADDED: `GetSplineAccelerationBezierQuad()` (#TBD) by @AmityWilder
+[rshapes] ADDED: `GetSplineAccelerationBezierCubic()` (#TBD) by @AmityWilder
+[rshapes] ADDED: `GetSplineJoltBezierCubic()` (#TBD) by @AmityWilder
+[rshapes] ADDED: `GetSplineBoundsBezierLinear()` (#TBD) by @AmityWilder
+[rshapes] ADDED: `GetSplineBoundsBezierQuad()` (#TBD) by @AmityWilder
+[rshapes] ADDED: `GetSplineBoundsBezierCubic()` (#TBD) by @AmityWilder
+[rshapes] ADDED: `GetSplineCurvatureBezierCubic()` (#TBD) by @AmityWilder
+[rshapes] ADDED: `GetSplineNearestTLinear()` (#TBD) by @AmityWilder
+[rshapes] ADDED: Example of `DrawSplineSegmentBezierCubicVar` in splines drawing example (#TBD) by @AmityWilder
 [rtextures] ADDED: `ColorIsEqual()` by @Ray
 [rtextures] ADDED: `ColorLerp()`, to mix 2 colors together (#4310) by @SusgUY446
 [rtextures] ADDED: `LoadImageAnimFromMemory()` (#3681) by @IoIxD

examples/shapes/shapes_splines_drawing.c

@@ -34,7 +34,8 @@ typedef enum {
     SPLINE_LINEAR = 0,      // Linear
     SPLINE_BASIS,           // B-Spline
     SPLINE_CATMULLROM,      // Catmull-Rom
-    SPLINE_BEZIER           // Cubic Bezier
+    SPLINE_BEZIER,          // Cubic Bezier
+    SPLINE_BEZIER_VAR       // Cubic Bezier, variable thickness
 } SplineType;
 
 //------------------------------------------------------------------------------------
@@ -78,7 +79,7 @@ int main(void)
 
     // Spline config variables
     float splineThickness = 8.0f;
-    int splineTypeActive = SPLINE_LINEAR; // 0-Linear, 1-BSpline, 2-CatmullRom, 3-Bezier
+    int splineTypeActive = SPLINE_BEZIER_VAR; // 0-Linear, 1-BSpline, 2-CatmullRom, 3-Bezier, 4-BezierVar
     bool splineTypeEditMode = false; 
     bool splineHelpersActive = true;
     
@@ -120,7 +121,7 @@ int main(void)
         }
         
         // Cubic Bezier spline control points logic
-        if ((splineTypeActive == SPLINE_BEZIER) && (focusedPoint == -1))
+        if (((splineTypeActive == SPLINE_BEZIER) || (splineTypeActive == SPLINE_BEZIER_VAR)) && (focusedPoint == -1))
         {
             // Spline control point focus and selection logic
             for (int i = 0; i < pointCount - 1; i++)
@@ -153,6 +154,7 @@ int main(void)
         else if (IsKeyPressed(KEY_TWO)) splineTypeActive = 1;
         else if (IsKeyPressed(KEY_THREE)) splineTypeActive = 2;
         else if (IsKeyPressed(KEY_FOUR)) splineTypeActive = 3;
+        else if (IsKeyPressed(KEY_FIVE)) splineTypeActive = 4;
         //----------------------------------------------------------------------------------
 
         // Draw
@@ -215,7 +217,36 @@ int main(void)
                     DrawSplineSegmentBezierCubic(pointsInterleaved[i], pointsInterleaved[i + 1], pointsInterleaved[i + 2], pointsInterleaved[i + 3], splineThickness, MAROON);
                 }
                 */
+            }
+            else if (splineTypeActive == SPLINE_BEZIER_VAR)
+            {
+                float thicks[] = {
+                    0.0f,
+                    splineThickness,
+                    splineThickness,
+                    0.0f,
+                };
 
+                // NOTE: Cubic-bezier spline requires the 2 control points of each segnment to be 
+                // provided interleaved with the start and end point of every segment
+                for (int i = 0; i < (pointCount - 1); i++) 
+                {
+                    pointsInterleaved[3*i] = points[i];
+                    pointsInterleaved[3*i + 1] = control[i].start;
+                    pointsInterleaved[3*i + 2] = control[i].end;
+                }
+                
+                pointsInterleaved[3*(pointCount - 1)] = points[pointCount - 1];
+
+                // Draw spline: cubic-bezier (with control points)
+                for (int i = 0; i < pointCount - 1; ++i)
+                {
+                    DrawSplineSegmentBezierCubicVar(points[i], control[i].start, control[i].end, points[i+1], thicks, 4, RED);
+                }
+            }
+
+            if ((splineTypeActive == SPLINE_BEZIER) || (splineTypeActive == SPLINE_BEZIER_VAR))
+            {
                 // Draw spline control points
                 for (int i = 0; i < pointCount - 1; i++)
                 {
@@ -242,6 +273,7 @@ int main(void)
                     DrawCircleLinesV(points[i], (focusedPoint == i)? 12.0f : 8.0f, (focusedPoint == i)? BLUE: DARKBLUE);
                     if ((splineTypeActive != SPLINE_LINEAR) &&
                         (splineTypeActive != SPLINE_BEZIER) &&
+                        (splineTypeActive != SPLINE_BEZIER_VAR) &&
                         (i < pointCount - 1)) DrawLineV(points[i], points[i + 1], GRAY);
 
                     DrawText(TextFormat("[%.0f, %.0f]", points[i].x, points[i].y), (int)points[i].x, (int)points[i].y + 10, 10, BLACK);
@@ -260,7 +292,7 @@ int main(void)
             GuiUnlock();
 
             GuiLabel((Rectangle){ 12, 10, 140, 24 }, "Spline type:");
-            if (GuiDropdownBox((Rectangle){ 12, 8 + 24, 140, 28 }, "LINEAR;BSPLINE;CATMULLROM;BEZIER", &splineTypeActive, splineTypeEditMode)) splineTypeEditMode = !splineTypeEditMode;
+            if (GuiDropdownBox((Rectangle){ 12, 8 + 24, 140, 28 }, "LINEAR;BSPLINE;CATMULLROM;BEZIER;BEZIER VARIABLE", &splineTypeActive, splineTypeEditMode)) splineTypeEditMode = !splineTypeEditMode;
 
         EndDrawing();
         //----------------------------------------------------------------------------------

src/raylib.h

@@ -1298,7 +1298,7 @@ RLAPI void DrawSplineSegmentBasis(Vector2 p1, Vector2 p2, Vector2 p3, Vector2 p4
 RLAPI void DrawSplineSegmentCatmullRom(Vector2 p1, Vector2 p2, Vector2 p3, Vector2 p4, float thick, Color color); // Draw spline segment: Catmull-Rom, 4 points
 RLAPI void DrawSplineSegmentBezierQuadratic(Vector2 p1, Vector2 c2, Vector2 p3, float thick, Color color); // Draw spline segment: Quadratic Bezier, 2 points, 1 control point
 RLAPI void DrawSplineSegmentBezierCubic(Vector2 p1, Vector2 c2, Vector2 c3, Vector2 p4, float thick, Color color); // Draw spline segment: Cubic Bezier, 2 points, 2 control points
-RLAPI void DrawSplineSegmentBezierCubicVar(Vector2 p1, Vector2 c2, Vector2 c3, Vector2 p4, const float* thicks, int thickCount, Color color); // Draw spline segment with variable thickness: Cubic Bezier, 2 points, 2 control points, 1 or more thickness
+RLAPI void DrawSplineSegmentBezierCubicVar(Vector2 p1, Vector2 c2, Vector2 c3, Vector2 p4, const float* thicks, int thickCount, Color color); // Draw spline segment with variable thickness: Cubic Bezier, 2 points, 2 control points
 
 // Spline segment point evaluation functions, for a given t [0.0f .. 1.0f]
 RLAPI Vector2 GetSplinePointLinear(Vector2 startPos, Vector2 endPos, float t);                           // Get (evaluate) spline point: Linear

src/rshapes.c

@@ -2107,63 +2107,93 @@ void DrawSplineSegmentBezierCubic(Vector2 p1, Vector2 c2, Vector2 c3, Vector2 p4
     DrawTriangleStrip(points, 2*SPLINE_SEGMENT_DIVISIONS + 2, color);
 }
 
-// Draw spline segment with variable thickness: Cubic Bezier, 2 points, 2 control points, 1 or more thickness
+// Draw spline segment with variable thickness: Cubic Bezier, 2 points, 2 control points
 void DrawSplineSegmentBezierCubicVar(Vector2 p1, Vector2 c2, Vector2 c3, Vector2 p4, const float* thicks, int thickCount, Color color)
 {
-    if (thickCount >= 1)
+    if (thickCount >= 4)
     {
+        rlBegin(RL_TRIANGLES);
+            rlColor4ub(color.r, color.g, color.b, color.a);
+
             const float step = 1.0f/SPLINE_SEGMENT_DIVISIONS;
 
-        Vector2 previous = p1;
+            Vector2 previous[2] = { 0 };
-        Vector2 current = { 0 };
+            Vector2 current[2] = { 0 };
             float t = 0.0f;
 
-        Vector2 points[2*SPLINE_SEGMENT_DIVISIONS + 2] = { 0 };
+            for (int i = 0; i <= SPLINE_SEGMENT_DIVISIONS; i++)
-
-        for (int i = 1; i <= SPLINE_SEGMENT_DIVISIONS; i++)
             {
                 t = step*(float)i;
 
-            float thick;
+                Vector2 tangent = { 0 };
-            if (thickCount > 1) {
+                {
-                float tMajor = t*(float)thickCount;
+                    float a = 3.0f*powf(1.0f - t, 2);
-                int tIndex = (int)tMajor;
+                    float b = 6.0f*(1.0f - t)*t;
-                if (tIndex >= thickCount) tIndex = thickCount - 1;
+                    float c = 3.0f*t*t;
-                float tMinor = tMajor - (float)tIndex;
+
-                thick = thicks[tIndex];
+                    tangent.x = a*(c2.x - p1.x) + b*(c3.x - c2.x) + c*(p4.x - c3.x);
-            } else {
+                    tangent.y = a*(c2.y - p1.y) + b*(c3.y - c2.y) + c*(p4.y - c3.y);
-                thick = thicks[0]; // constant thickness
                 }
 
+                float speedSqr = (tangent.x*tangent.x + tangent.y*tangent.y);
+                if (speedSqr == 0) continue;
+                float speedInv = 1.0f/sqrtf(speedSqr);
+                tangent.x = tangent.x*speedInv;
+                tangent.y = tangent.y*speedInv;
+
+                Vector2 point = { 0 };
+                {
                     float a = powf(1.0f - t, 3);
                     float b = 3.0f*powf(1.0f - t, 2)*t;
                     float c = 3.0f*(1.0f - t)*powf(t, 2);
                     float d = powf(t, 3);
 
-            current.y = a*p1.y + b*c2.y + c*c3.y + d*p4.y;
+                    point.y = a*p1.y + b*c2.y + c*c3.y + d*p4.y;
-            current.x = a*p1.x + b*c2.x + c*c3.x + d*p4.x;
+                    point.x = a*p1.x + b*c2.x + c*c3.x + d*p4.x;
+                }
 
-            float dy = current.y - previous.y;
+                // TODO: Doesn't seem to be working properly for more than 3 distinct values
-            float dx = current.x - previous.x;
+                float thick;
-            float size = 0.5f*thick/sqrtf(dx*dx+dy*dy);
-
-            if (i == 1)
                 {
-                points[0].x = previous.x + dy*size;
+                    float tMajor = t*(float)thickCount;
-                points[0].y = previous.y - dx*size;
+                    int tIndex = (int)tMajor;
-                points[1].x = previous.x - dy*size;
+                    float tMinor = tMajor - (float)tIndex;
-                points[1].y = previous.y + dx*size;
+                    tIndex *= 3;
+                    if (tIndex >= thickCount - 3)
+                    {
+                        tIndex = thickCount - 4;
+                        tMinor = 1.0f;
+                    }
+                    float a = powf(1.0f - t, 3);
+                    float b = 3.0f*powf(1.0f - t, 2)*t;
+                    float c = 3.0f*(1.0f - t)*t*t;
+                    float d = t*t*t;
+
+                    thick = a*thicks[tIndex] + b*thicks[tIndex + 1] + c*thicks[tIndex + 2] + d*thicks[tIndex + 3];
                 }
 
-            points[2*i + 1].x = current.x - dy*size;
+                current[0].x = point.x + thick*tangent.y;
-            points[2*i + 1].y = current.y + dx*size;
+                current[0].y = point.y - thick*tangent.x;
-            points[2*i].x = current.x + dy*size;
-            points[2*i].y = current.y - dx*size;
 
-            previous = current;
+                current[1].x = point.x - thick*tangent.y;
+                current[1].y = point.y + thick*tangent.x;
+
+                if (i > 0)
+                {
+                    rlVertex2f(current[0].x, current[0].y);
+                    rlVertex2f(previous[0].x, previous[0].y);
+                    rlVertex2f(previous[1].x, previous[1].y);
+
+                    rlVertex2f(current[1].x, current[1].y);
+                    rlVertex2f(current[0].x, current[0].y);
+                    rlVertex2f(previous[1].x, previous[1].y);
                 }
 
-        DrawTriangleStrip(points, 2*SPLINE_SEGMENT_DIVISIONS + 2, color);
+                previous[0] = current[0];
+                previous[1] = current[1];
+            }
+
+        rlEnd();
     }
 }
 
@@ -2576,7 +2606,7 @@ float GetSplineCurvatureBezierCubic(Vector2 startPos, Vector2 startControlPos, V
     acceleration.x = a*(endControlPos.x - 2.0f*startControlPos.x + startPos.x) + b*(endPos.x - 2.0f*endControlPos.x + startControlPos.x);
     acceleration.y = a*(endControlPos.y - 2.0f*startControlPos.y + startPos.y) + b*(endPos.y - 2.0f*endControlPos.y + startControlPos.y);
 
-    float curvature = (velocity.x*acceleration.y - velocity.y*acceleration.x)/powf(sqrtf(velocity.x*velocity.x + velocity.y*velocity.y), 3);
+    curvature = (velocity.x*acceleration.y - velocity.y*acceleration.x)/powf(sqrtf(velocity.x*velocity.x + velocity.y*velocity.y), 3);
 
     return curvature;
 }