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solid sphere now done with only triangle strips.

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All shapes should be doable with only triangle strips, so this allows
code reuse later ...



git-svn-id: https://svn.code.sf.net/p/freeglut/code/trunk@1249 7f0cb862-5218-0410-a997-914c9d46530a
This commit is contained in:
dcnieho 2012-04-20 11:25:42 +00:00
parent 6a17bac02a
commit b66ef56d4b
1 changed files with 33 additions and 38 deletions
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71
freeglut/freeglut/src/fg_geometry.c
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@ -1074,55 +1074,56 @@ static void fghSphere( double radius, GLint slices, GLint stacks, GLboolean useW
}
else
{
GLushort *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.
* All stacks, including top and bottom are covered with a triangle
* strip.
*/
GLushort *stripIdx;
/* Create index vector */
GLushort offset;
/* Allocate buffers for indices, bail out if memory allocation fails */
topIdx = malloc((slices+2)*sizeof(GLushort));
bottomIdx = malloc((slices+2)*sizeof(GLushort));
stripIdx = malloc((slices+1)*2*(stacks-2)*sizeof(GLushort));
if (!(topIdx) || !(bottomIdx) || !(stripIdx))
stripIdx = malloc((slices+1)*2*(stacks)*sizeof(GLushort));
if (!(stripIdx))
{
free(topIdx);
free(bottomIdx);
free(stripIdx);
fgError("Failed to allocate memory in fghGenerateSphere");
}
/* TODO: Can do top and bottom as Triangle strip as well
(just need to repeat top/btoom vertex a lot). Then we can draw
the whole thing with just one index array and one for-looped call
to glDrawElements.. That'll make it easier to reuse code with other
Circular objects too
*/
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;
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 */
/* 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)
/* top stack */
for (j=0, idx=0; j<slices; j++, idx+=2)
{
GLushort offset = 1+i*slices; /* triangle_strip indices start at 1 (0 is top vertex), and we advance one stack down as we go along */
stripIdx[idx ] = j+1; /* 0 is top vertex, 1 is first for first stack */
stripIdx[idx+1] = 0;
}
stripIdx[idx ] = 1; /* repeat first slice's idx for closing off shape */
stripIdx[idx+1] = 0;
idx+=2;
/* middle stacks: */
/* Strip indices are relative to first index belonging to strip, NOT relative to first vertex/normal pair in array */
for (i=0; i<stacks-2; i++, idx+=2)
{
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)
{
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;
stripIdx[idx+1] = offset;
}
/* bottom stack */
offset = 1+(stacks-2)*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)
{
stripIdx[idx ] = nVert-1; /* zero based index, last element in array (bottom vertex)... */
stripIdx[idx+1] = offset+j;
}
stripIdx[idx ] = nVert-1; /* repeat first slice's idx for closing off shape */
stripIdx[idx+1] = offset;
/* draw */
glEnableClientState(GL_VERTEX_ARRAY);
@ -1130,20 +1131,14 @@ static void fghSphere( double radius, GLint slices, GLint stacks, GLboolean useW
glVertexPointer(3, GL_FLOAT, 0, vertices);
glNormalPointer(GL_FLOAT, 0, normals);
/*draw top*/
glDrawElements(GL_TRIANGLE_FAN,slices+2,GL_UNSIGNED_SHORT,topIdx);
/*draw stacks*/
for (i=0; i<stacks-2; i++)
for (i=0; i<stacks; i++)
glDrawElements(GL_TRIANGLE_STRIP,(slices+1)*2,GL_UNSIGNED_SHORT,stripIdx+i*(slices+1)*2);
/*draw bottom*/
glDrawElements(GL_TRIANGLE_FAN,slices+2,GL_UNSIGNED_SHORT,bottomIdx);
glDisableClientState(GL_VERTEX_ARRAY);
glDisableClientState(GL_NORMAL_ARRAY);
/* cleanup allocated memory */
free(topIdx);
free(bottomIdx);
free(stripIdx);
}