From 13e309251184343b67773d16e6e264c7cac7c280 Mon Sep 17 00:00:00 2001
From: Ray <raysan5@gmail.com>
Date: Sun, 30 Jun 2024 11:15:45 +0200
Subject: [PATCH] REVIEWED: `DrawSphereEx()`, added educational info

---
 src/rmodels.c | 60 ++++++++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 52 insertions(+), 8 deletions(-)

diff --git a/src/rmodels.c b/src/rmodels.c
index 6de27021e007..b67c8e695650 100644
--- a/src/rmodels.c
+++ b/src/rmodels.c
@@ -424,6 +424,48 @@ void DrawSphere(Vector3 centerPos, float radius, Color color)
 // Draw sphere with extended parameters
 void DrawSphereEx(Vector3 centerPos, float radius, int rings, int slices, Color color)
 {
+#if 0
+    // Basic implementation, do not use it!
+    // For a sphere with 16 rings and 16 slices it requires 8640 cos()/sin() function calls! 
+    // New optimized version below only requires 4 cos()/sin() calls
+    
+    rlPushMatrix();
+        // NOTE: Transformation is applied in inverse order (scale -> translate)
+        rlTranslatef(centerPos.x, centerPos.y, centerPos.z);
+        rlScalef(radius, radius, radius);
+        
+        rlBegin(RL_TRIANGLES);
+            rlColor4ub(color.r, color.g, color.b, color.a);
+
+            for (int i = 0; i < (rings + 2); i++)
+            {
+                for (int j = 0; j < slices; j++)
+                {
+                    rlVertex3f(cosf(DEG2RAD*(270 + (180.0f/(rings + 1))*i))*sinf(DEG2RAD*(360.0f*j/slices)),
+                               sinf(DEG2RAD*(270 + (180.0f/(rings + 1))*i)),
+                               cosf(DEG2RAD*(270 + (180.0f/(rings + 1))*i))*cosf(DEG2RAD*(360.0f*j/slices)));
+                    rlVertex3f(cosf(DEG2RAD*(270 + (180.0f/(rings + 1))*(i + 1)))*sinf(DEG2RAD*(360.0f*(j + 1)/slices)),
+                               sinf(DEG2RAD*(270 + (180.0f/(rings + 1))*(i + 1))),
+                               cosf(DEG2RAD*(270 + (180.0f/(rings + 1))*(i + 1)))*cosf(DEG2RAD*(360.0f*(j + 1)/slices)));
+                    rlVertex3f(cosf(DEG2RAD*(270 + (180.0f/(rings + 1))*(i + 1)))*sinf(DEG2RAD*(360.0f*j/slices)),
+                               sinf(DEG2RAD*(270 + (180.0f/(rings + 1))*(i + 1))),
+                               cosf(DEG2RAD*(270 + (180.0f/(rings + 1))*(i + 1)))*cosf(DEG2RAD*(360.0f*j/slices)));
+
+                    rlVertex3f(cosf(DEG2RAD*(270 + (180.0f/(rings + 1))*i))*sinf(DEG2RAD*(360.0f*j/slices)),
+                               sinf(DEG2RAD*(270 + (180.0f/(rings + 1))*i)),
+                               cosf(DEG2RAD*(270 + (180.0f/(rings + 1))*i))*cosf(DEG2RAD*(360.0f*j/slices)));
+                    rlVertex3f(cosf(DEG2RAD*(270 + (180.0f/(rings + 1))*(i)))*sinf(DEG2RAD*(360.0f*(j + 1)/slices)),
+                               sinf(DEG2RAD*(270 + (180.0f/(rings + 1))*(i))),
+                               cosf(DEG2RAD*(270 + (180.0f/(rings + 1))*(i)))*cosf(DEG2RAD*(360.0f*(j + 1)/slices)));
+                    rlVertex3f(cosf(DEG2RAD*(270 + (180.0f/(rings + 1))*(i + 1)))*sinf(DEG2RAD*(360.0f*(j + 1)/slices)),
+                               sinf(DEG2RAD*(270 + (180.0f/(rings + 1))*(i + 1))),
+                               cosf(DEG2RAD*(270 + (180.0f/(rings + 1))*(i + 1)))*cosf(DEG2RAD*(360.0f*(j + 1)/slices)));
+                }
+            }
+        rlEnd();
+    rlPopMatrix();
+#endif
+
     rlPushMatrix();
         // NOTE: Transformation is applied in inverse order (scale -> translate)
         rlTranslatef(centerPos.x, centerPos.y, centerPos.z);
@@ -440,16 +482,18 @@ void DrawSphereEx(Vector3 centerPos, float radius, int rings, int slices, Color
             float cosslice = cosf(sliceangle);
             float sinslice = sinf(sliceangle);
 
-            Vector3 vertices[4]; // Store face vertices
-            vertices[2] = (Vector3){0,1,0};
-            vertices[3] = (Vector3){sinring, cosring, 0};
+            Vector3 vertices[4] = { 0 }; // Required to store face vertices
+            vertices[2] = (Vector3){ 0, 1, 0 };
+            vertices[3] = (Vector3){ sinring, cosring, 0 };
 
-            for (int i = 0; i < rings + 1; i++) {
-                for (int j = 0; j < slices; j++) {
+            for (int i = 0; i < rings + 1; i++)
+            {
+                for (int j = 0; j < slices; j++) 
+                {
                     vertices[0] = vertices[2]; // Rotate around y axis to set up vertices for next face
                     vertices[1] = vertices[3];
-                    vertices[2] = (Vector3){cosslice*vertices[2].x - sinslice*vertices[2].z, vertices[2].y, sinslice*vertices[2].x + cosslice*vertices[2].z}; // Rotation matrix around y axis
-                    vertices[3] = (Vector3){cosslice*vertices[3].x - sinslice*vertices[3].z, vertices[3].y, sinslice*vertices[3].x + cosslice*vertices[3].z};
+                    vertices[2] = (Vector3){ cosslice*vertices[2].x - sinslice*vertices[2].z, vertices[2].y, sinslice*vertices[2].x + cosslice*vertices[2].z }; // Rotation matrix around y axis
+                    vertices[3] = (Vector3){ cosslice*vertices[3].x - sinslice*vertices[3].z, vertices[3].y, sinslice*vertices[3].x + cosslice*vertices[3].z };
 
                     rlVertex3f(vertices[0].x, vertices[0].y, vertices[0].z);
                     rlVertex3f(vertices[3].x, vertices[3].y, vertices[3].z);
@@ -461,7 +505,7 @@ void DrawSphereEx(Vector3 centerPos, float radius, int rings, int slices, Color
                 }
 
                 vertices[2] = vertices[3]; // Rotate around z axis to set up  starting vertices for next ring
-                vertices[3] = (Vector3){cosring*vertices[3].x + sinring*vertices[3].y, -sinring*vertices[3].x + cosring*vertices[3].y, vertices[3].z}; // Rotation matrix around z axis
+                vertices[3] = (Vector3){ cosring*vertices[3].x + sinring*vertices[3].y, -sinring*vertices[3].x + cosring*vertices[3].y, vertices[3].z }; // Rotation matrix around z axis
             }
         rlEnd();
     rlPopMatrix();