From b728f245550aed93c5e33dbccb58ced002f41959 Mon Sep 17 00:00:00 2001
From: Diederick Niehorster <dcnieho@gmail.com>
Date: Sun, 25 Mar 2012 10:13:52 +0000
Subject: [PATCH] ported sphere. Drawing code is still in the sphere function,
 that and the vertex index generating code can hopefully be
 abstracted away. But first need to port the other shapes so
 I have a better idea of the overlap. (sorry Sylvain! Just
 don't touch the sphere for now)

git-svn-id: svn+ssh://svn.code.sf.net/p/freeglut/code/trunk/freeglut/freeglut@1209 7f0cb862-5218-0410-a997-914c9d46530a
---
 src/fg_geometry.c |  337 +++++++++++++++++++++++++++++++++--------------------
 1 file changed, 209 insertions(+), 128 deletions(-)

diff --git a/src/fg_geometry.c b/src/fg_geometry.c
index ccbe5d7..438d447 100644
--- a/src/fg_geometry.c
+++ b/src/fg_geometry.c
@@ -60,8 +60,8 @@ static void fghDrawGeometryWire(GLfloat *vertices, GLfloat *normals, GLsizei num
     glDisableClientState(GL_VERTEX_ARRAY);
     glDisableClientState(GL_NORMAL_ARRAY);
 }
-/**
- * Draw the geometric shape with filled triangles
+
+/* 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.
@@ -86,6 +86,8 @@ static void fghDrawGeometrySolid(GLfloat *vertices, GLfloat *normals, GLubyte *v
     glDisableClientState(GL_NORMAL_ARRAY);
 }
 
+
+
 /* 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
@@ -632,6 +634,81 @@ static void fghCircleTable(GLfloat **sint, GLfloat **cost, const int n, const GL
     }
 }
 
+static void fghGenerateSphere(GLfloat radius, GLint slices, GLint stacks, GLfloat **vertices, GLfloat **normals, int* nVert)
+{
+    int i,j;
+    int idx = 0;    /* idx into vertex/normal buffer */
+    GLfloat x,y,z;
+
+    /* Pre-computed circle */
+    GLfloat *sint1,*cost1;
+    GLfloat *sint2,*cost2;
+
+    /* number of unique vertices */
+    if (slices==0 || stacks<2)
+    {
+        /* nothing to generate */
+        *nVert = 0;
+        return;
+    }
+    *nVert = slices*(stacks-1)+2;
+
+    /* precompute values on unit circle */
+    fghCircleTable(&sint1,&cost1,-slices,FALSE);
+    fghCircleTable(&sint2,&cost2, stacks,TRUE);
+
+    /* Allocate vertex and normal buffers, bail out if memory allocation fails */
+    *vertices = malloc((*nVert)*3*sizeof(GLfloat));
+    *normals  = malloc((*nVert)*3*sizeof(GLfloat));
+    if (!(vertices) || !(normals))
+    {
+        free(*vertices);
+        free(*normals);
+        fgError("Failed to allocate memory in fghGenerateSphere");
+    }
+
+    /* top */
+    (*vertices)[0] = 0.f;
+    (*vertices)[1] = 0.f;
+    (*vertices)[2] = radius;
+    (*normals )[0] = 0.f;
+    (*normals )[1] = 0.f;
+    (*normals )[2] = 1.f;
+    idx = 3;
+
+    /* each stack */
+    for( i=1; i<stacks; i++ )
+    {
+        for(j=0; j<slices; j++, idx+=3)
+        {
+            x = cost1[j]*sint2[i];
+            y = sint1[j]*sint2[i];
+            z = cost2[i];
+
+            (*vertices)[idx  ] = x*radius;
+            (*vertices)[idx+1] = y*radius;
+            (*vertices)[idx+2] = z*radius;
+            (*normals )[idx  ] = x;
+            (*normals )[idx+1] = y;
+            (*normals )[idx+2] = z;
+        }
+    }
+
+    /* bottom */
+    (*vertices)[idx  ] =  0.f;
+    (*vertices)[idx+1] =  0.f;
+    (*vertices)[idx+2] = -radius;
+    (*normals )[idx  ] =  0.f;
+    (*normals )[idx+1] =  0.f;
+    (*normals )[idx+2] = -1.f;
+
+    /* Done creating vertices, release sin and cos tables */
+    free(sint1);
+    free(cost1);
+    free(sint2);
+    free(cost2);
+}
+
 
 /* -- INTERNAL DRAWING functions --------------------------------------- */
 #define _DECLARE_INTERNAL_DRAW_DO_DECLARE(name,nameICaps,nameCaps,vertIdxs)\
@@ -739,99 +816,162 @@ static void fghSierpinskiSponge ( int numLevels, double offset[3], GLfloat scale
         free(normals );
     }
 }
-#endif /* GL_ES_VERSION_2_0 */
 
 
-/* -- INTERFACE FUNCTIONS ---------------------------------------------- */
-
-
-#ifndef EGL_VERSION_1_0
-/*
- * Draws a solid sphere
- */
-void FGAPIENTRY glutSolidSphere(double radius, GLint slices, GLint stacks)
+static void fghSphere( double radius, GLint slices, GLint stacks, GLboolean useWireMode )
 {
-    int i,j;
+    int i,j,idx, nVert;
+    GLfloat *vertices, *normals;
 
-    /* Adjust z and radius as stacks are drawn. */
-    GLfloat radf = (GLfloat)radius;
-    GLfloat z0,z1;
-    GLfloat r0,r1;
-
-    /* Pre-computed circle */
+    /* Generate vertices and normals */
+    fghGenerateSphere((GLfloat)radius,slices,stacks,&vertices,&normals,&nVert);
+    
+    if (nVert==0)
+        /* nothing to draw */
+        return;
 
-    GLfloat *sint1,*cost1;
-    GLfloat *sint2,*cost2;
+    if (useWireMode)
+    {
+        GLuint  *sliceIdx, *stackIdx;
+        /* First, generate vertex index arrays for drawing with glDrawElements
+         * We have a bunch of line_loops to draw for each stack, and a
+         * bunch for each slice.
+         */
 
-    FREEGLUT_EXIT_IF_NOT_INITIALISED ( "glutSolidSphere" );
+        sliceIdx = malloc(slices*(stacks+1)*sizeof(GLuint));
+        stackIdx = malloc(slices*(stacks-1)*sizeof(GLuint));
 
-    fghCircleTable(&sint1,&cost1,-slices,FALSE);
-    fghCircleTable(&sint2,&cost2, stacks,TRUE);
+        /* generate for each stack */
+        for (i=0,idx=0; i<slices; i++)
+        {
+            GLuint offset = 1+i;                    /* start at 1 (0 is top vertex), and we advance one slice as we go along */
+            sliceIdx[idx++] = 0;                    /* vertex on top */
+            for (j=0; j<stacks-1; j++, idx++)
+            {
+                sliceIdx[idx] = offset+j*slices;
+            }
+            sliceIdx[idx++] = nVert-1;              /* zero based index, last element in array... */
+        }
 
-    /* The top stack is covered with a triangle fan */
+        /* generate for each stack */
+        for (i=0,idx=0; i<stacks-1; i++)
+        {
+            GLuint offset = 1+i*slices;             /* start at 1 (0 is top vertex), and we advance one stack down as we go along */
+            for (j=0; j<slices; j++, idx++)
+            {
+                stackIdx[idx] = offset+j;
+            }
+        }
 
-    z0 = 1;
-    z1 = cost2[(stacks>0)?1:0];
-    r0 = 0;
-    r1 = sint2[(stacks>0)?1:0];
+        /* draw */
+        glEnableClientState(GL_VERTEX_ARRAY);
+        glEnableClientState(GL_NORMAL_ARRAY);
 
-    glBegin(GL_TRIANGLE_FAN);
+        glVertexPointer(3, GL_FLOAT, 0, vertices);
+        glNormalPointer(GL_FLOAT, 0, normals);
+        /*draw slices*/
+        for (i=0; i<slices; i++)
+            glDrawElements(GL_LINE_STRIP,stacks+1,GL_UNSIGNED_INT,sliceIdx+i*(stacks+1));
+        /*draw stacks*/
+        for (i=0; i<stacks-1; i++)
+            glDrawElements(GL_LINE_LOOP, slices,GL_UNSIGNED_INT,stackIdx+i*slices);
 
-        glNormal3f(0,0,1);
-        glVertex3f(0,0,radf);
+        glDisableClientState(GL_VERTEX_ARRAY);
+        glDisableClientState(GL_NORMAL_ARRAY);
 
-        for (j=slices; j>=0; j--)
+        /* cleanup allocated memory */
+        free(sliceIdx);
+        free(stackIdx);
+    }
+    else
+    {
+        GLuint  *topIdx, *bottomIdx, *stripIdx;
+        /* First, generate vertex index arrays for drawing with glDrawElements
+         * Top and bottom are covered with a triangle fan
+         * Each other stack with triangle strip. Only need to generate on
+         * of those as we'll have to draw each stack separately, and can
+         * just use different offsets in glDrawElements.
+         */
+
+        /* Allocate buffers for indices, bail out if memory allocation fails */
+        topIdx = malloc((slices+2)*sizeof(GLuint));
+        bottomIdx = malloc((slices+2)*sizeof(GLuint));
+        stripIdx = malloc((slices+1)*2*(stacks-2)*sizeof(GLuint));
+        if (!(topIdx) || !(bottomIdx) || !(stripIdx))
         {
-            glNormal3f(cost1[j]*r1,      sint1[j]*r1,      z1     );
-            glVertex3f(cost1[j]*r1*radf, sint1[j]*r1*radf, z1*radf);
+            free(topIdx);
+            free(bottomIdx);
+            free(stripIdx);
+            fgError("Failed to allocate memory in fghGenerateSphere");
         }
 
-    glEnd();
+        topIdx[0]=0;
+        topIdx[1] = 1;                              /* repeat first slice's idx for closing off shape */
+        for (j=slices, idx=2; j>0; j--, idx++)
+            topIdx[idx] = j;
 
-    /* Cover each stack with a quad strip, except the top and bottom stacks */
-
-    for( i=1; i<stacks-1; i++ )
-    {
-        z0 = z1; z1 = cost2[i+1];
-        r0 = r1; r1 = sint2[i+1];
-
-        glBegin(GL_QUAD_STRIP);
+        bottomIdx[0]=nVert-1;                       /* zero based index, last element in array... */
+        for (j=0, idx=1; j<slices; j++, idx++)
+            bottomIdx[idx] = nVert-(slices+1)+j;
+        bottomIdx[idx] = nVert-(slices+1);          /* repeat first slice's idx for closing off shape */
 
-            for(j=0; j<=slices; j++)
+        /* Strip indices are relative to first index belonging to strip, NOT relative to first vertex/normal pair in array */
+        for (i=0,idx=0; i<stacks-2; i++, idx+=2)
+        {
+            GLuint offset = 1+i*slices;             /* triangle_strip indices start at 1 (0 is top vertex), and we advance one stack down as we go along */
+            for (j=0; j<slices; j++, idx+=2)
             {
-                glNormal3d(cost1[j]*r1,      sint1[j]*r1,      z1     );
-                glVertex3d(cost1[j]*r1*radf, sint1[j]*r1*radf, z1*radf);
-                glNormal3d(cost1[j]*r0,      sint1[j]*r0,      z0     );
-                glVertex3d(cost1[j]*r0*radf, sint1[j]*r0*radf, z0*radf);
+                stripIdx[idx  ] = offset+j+slices;
+                stripIdx[idx+1] = offset+j;
             }
+            stripIdx[idx  ] = offset+slices;        /* repeat first slice's idx for closing off shape */
+            stripIdx[idx+1] = offset+0;
+        }
 
-        glEnd();
-    }
 
-    /* The bottom stack is covered with a triangle fan */
+        /* draw */
+        glEnableClientState(GL_VERTEX_ARRAY);
+        glEnableClientState(GL_NORMAL_ARRAY);
 
-    z0 = z1;
-    r0 = r1;
+        glVertexPointer(3, GL_FLOAT, 0, vertices);
+        glNormalPointer(GL_FLOAT, 0, normals);
+        /*draw top*/
+        glDrawElements(GL_TRIANGLE_FAN,slices+2,GL_UNSIGNED_INT,topIdx);
+        /*draw stacks*/
+        for (i=0; i<stacks-2; i++)
+            glDrawElements(GL_TRIANGLE_STRIP,(slices+1)*2,GL_UNSIGNED_INT,stripIdx+i*(slices+1)*2);
+        /*draw bottom*/
+        glDrawElements(GL_TRIANGLE_FAN,slices+2,GL_UNSIGNED_INT,bottomIdx);
 
-    glBegin(GL_TRIANGLE_FAN);
+        glDisableClientState(GL_VERTEX_ARRAY);
+        glDisableClientState(GL_NORMAL_ARRAY);
 
-        glNormal3d(0,0,-1);
-        glVertex3d(0,0,-radius);
+        /* cleanup allocated memory */
+        free(topIdx);
+        free(bottomIdx);
+        free(stripIdx);
+    }
+    
+    /* cleanup allocated memory */
+    free(vertices);
+    free(normals);
+}
 
-        for (j=0; j<=slices; j++)
-        {
-            glNormal3d(cost1[j]*r0,      sint1[j]*r0,      z0     );
-            glVertex3d(cost1[j]*r0*radf, sint1[j]*r0*radf, z0*radf);
-        }
+#endif /* GL_ES_VERSION_2_0 */
 
-    glEnd();
 
-    /* Release sin and cos tables */
+/* -- INTERFACE FUNCTIONS ---------------------------------------------- */
 
-    free(sint1);
-    free(cost1);
-    free(sint2);
-    free(cost2);
+
+#ifndef EGL_VERSION_1_0
+/*
+ * Draws a solid sphere
+ */
+void FGAPIENTRY glutSolidSphere(double radius, GLint slices, GLint stacks)
+{
+    FREEGLUT_EXIT_IF_NOT_INITIALISED ( "glutSolidSphere" );
+
+    fghSphere( radius, slices, stacks, FALSE );
 }
 
 /*
@@ -839,69 +979,10 @@ void FGAPIENTRY glutSolidSphere(double radius, GLint slices, GLint stacks)
  */
 void FGAPIENTRY glutWireSphere(double radius, GLint slices, GLint stacks)
 {
-    int i,j;
-
-    /* Adjust z and radius as stacks and slices are drawn. */
-    GLfloat radf = (GLfloat)radius;
-    GLfloat r;
-    GLfloat x,y,z;
-
-    /* Pre-computed circle */
-
-    GLfloat *sint1,*cost1;
-    GLfloat *sint2,*cost2;
-
     FREEGLUT_EXIT_IF_NOT_INITIALISED ( "glutWireSphere" );
 
-    fghCircleTable(&sint1,&cost1,-slices,FALSE);
-    fghCircleTable(&sint2,&cost2, stacks,TRUE);
-
-    /* Draw a line loop for each stack */
-
-    for (i=1; i<stacks; i++)
-    {
-        z = cost2[i];
-        r = sint2[i];
-
-        glBegin(GL_LINE_LOOP);
-
-            for(j=0; j<=slices; j++)
-            {
-                x = cost1[j];
-                y = sint1[j];
-
-                glNormal3f(x,y,z);
-                glVertex3f(x*r*radf,y*r*radf,z*radf);
-            }
-
-        glEnd();
-    }
-
-    /* Draw a line loop for each slice */
-
-    for (i=0; i<slices; i++)
-    {
-        glBegin(GL_LINE_STRIP);
-
-            for(j=0; j<=stacks; j++)
-            {
-                x = cost1[i]*sint2[j];
-                y = sint1[i]*sint2[j];
-                z = cost2[j];
-
-                glNormal3f(x,y,z);
-                glVertex3f(x*radf,y*radf,z*radf);
-            }
-
-        glEnd();
-    }
-
-    /* Release sin and cos tables */
-
-    free(sint1);
-    free(cost1);
-    free(sint2);
-    free(cost2);
+    fghSphere( radius, slices, stacks, TRUE );
+    
 }
 
 /*
-- 
1.7.10.4