Add documentation for geometry (ML rip-off) and Android corner-cases

[freeglut] / src / fg_geometry.c

diff --git a/src/fg_geometry.c b/src/fg_geometry.c
index 4811ee5..0ab14ac 100644 (file)
--- a/src/fg_geometry.c
+++ b/src/fg_geometry.c
@@ -55,6 +55,8 @@
  * from face to face.
  */
 
+/** See comment for fghDrawGeometryWire **/
+
 /* Version for OpenGL (ES) 1.1 */
 #ifndef GL_ES_VERSION_2_0
 static void fghDrawGeometryWire11(GLfloat *vertices, GLfloat *normals,
@@ -166,7 +168,8 @@ static void fghDrawGeometryWire20(GLfloat *vertices, GLfloat *normals, GLsizei n
     } else {
         fghBindBuffer(FGH_ELEMENT_ARRAY_BUFFER, ibo_elements);
         for (i=0; i<numParts; i++)
-            glDrawElements(vertexMode,numVertPerPart,GL_UNSIGNED_SHORT,(void*)(long)(i*numVertPerPart));
+            glDrawElements(vertexMode, numVertPerPart,
+                           GL_UNSIGNED_SHORT, (GLvoid*)(sizeof(vertIdxs[0])*i*numVertPerPart));
         /* Clean existing bindings before clean-up */
         /* Android showed instability otherwise */
         fghBindBuffer(FGH_ELEMENT_ARRAY_BUFFER, 0);
@@ -175,7 +178,8 @@ static void fghDrawGeometryWire20(GLfloat *vertices, GLfloat *normals, GLsizei n
     if (vertIdxs2) {
         fghBindBuffer(FGH_ELEMENT_ARRAY_BUFFER, ibo_elements2);
         for (i=0; i<numParts2; i++)
-            glDrawElements(GL_LINE_LOOP,numVertPerPart2,GL_UNSIGNED_SHORT,(void*)(long)(i*numVertPerPart2));
+            glDrawElements(GL_LINE_LOOP, numVertPerPart2,
+                           GL_UNSIGNED_SHORT, (GLvoid*)(sizeof(vertIdxs2[0])*i*numVertPerPart2));
         /* Clean existing bindings before clean-up */
         /* Android showed instability otherwise */
         fghBindBuffer(FGH_ELEMENT_ARRAY_BUFFER, 0);
@@ -196,6 +200,20 @@ static void fghDrawGeometryWire20(GLfloat *vertices, GLfloat *normals, GLsizei n
         fghDeleteBuffers(1, &ibo_elements2);
 }
 
+/**
+ * Draw geometric shape in wire mode (only edges)
+ *
+ * Arguments: the sphere, in wire mode, consists of multiple line
+ * loops for the stacks, and for the slices. The vertex indices for
+ * all slices are thrown together. numParts is how many separate loops
+ * are in the array, numVertIdxsPerPart is how many vertices there are
+ * per loop.  For those suffixed with 2, its exactly the same
+ * principle, the number of stacks and slices is not the same.
+ *
+ * Feel free to contribute better naming ;)
+ *
+ * See comment for fghDrawGeometrySolid
+ */
 static void fghDrawGeometryWire(GLfloat *vertices, GLfloat *normals, GLsizei numVertices,
     GLushort *vertIdxs, GLsizei numParts, GLsizei numVertPerPart, GLenum vertexMode,
     GLushort *vertIdxs2, GLsizei numParts2, GLsizei numVertPerPart2
@@ -219,15 +237,6 @@ static void fghDrawGeometryWire(GLfloat *vertices, GLfloat *normals, GLsizei num
 }
 
 
-/* Draw the geometric shape with filled triangles
- *
- * - If the shape is naturally triangulated (numEdgePerFace==3), each
- *   vertex+normal pair is used only once, so no vertex indices.
- * 
- * - If the shape was triangulated (DECOMPOSE_TO_TRIANGLE), some
- *   vertex+normal pairs are reused, so use vertex indices.
- */
-
 /* Version for OpenGL (ES) 1.1 */
 #ifndef GL_ES_VERSION_2_0
 static void fghDrawGeometrySolid11(GLfloat *vertices, GLfloat *normals, GLushort *vertIdxs,
@@ -321,7 +330,7 @@ static void fghDrawGeometrySolid20(GLfloat *vertices, GLfloat *normals, GLushort
         fghBindBuffer(FGH_ELEMENT_ARRAY_BUFFER, ibo_elements);
         if (numParts>1) {
             for (i=0; i<numParts; i++) {
-                glDrawElements(GL_TRIANGLE_STRIP, numVertIdxsPerPart, GL_UNSIGNED_SHORT, (void*)(long)(i*numVertIdxsPerPart));
+                glDrawElements(GL_TRIANGLE_STRIP, numVertIdxsPerPart, GL_UNSIGNED_SHORT, (GLvoid*)(sizeof(vertIdxs[0])*i*numVertIdxsPerPart));
             }
         } else {
             glDrawElements(GL_TRIANGLES, numVertIdxsPerPart, GL_UNSIGNED_SHORT, 0);
@@ -344,6 +353,14 @@ static void fghDrawGeometrySolid20(GLfloat *vertices, GLfloat *normals, GLushort
         fghDeleteBuffers(1, &ibo_elements);
 }
 
+/* Draw the geometric shape with filled triangles
+ *
+ * - If the shape is naturally triangulated (numEdgePerFace==3), each
+ *   vertex+normal pair is used only once, so no vertex indices.
+ * 
+ * - If the shape was triangulated (DECOMPOSE_TO_TRIANGLE), some
+ *   vertex+normal pairs are reused, so use vertex indices.
+ */
 static void fghDrawGeometrySolid(GLfloat *vertices, GLfloat *normals, GLushort *vertIdxs,
                                  GLsizei numVertices, GLsizei numParts, GLsizei numVertIdxsPerPart)
 {
@@ -362,6 +379,8 @@ static void fghDrawGeometrySolid(GLfloat *vertices, GLfloat *normals, GLushort *
 #endif
 }
 
+
+
 /* Shape decomposition to triangles
  * We'll use glDrawElements to draw all shapes that are not naturally
  * composed of triangles, so generate an index vector here, using the