maybe you guys can uncode something like this to explain the error:
/*
=====================
Autosprite2Deform
Autosprite2 will pivot a rectangular quad along the center of its long axis
=====================
*/
int edgeVerts[6][2] = {
{ 0, 1 },
{ 0, 2 },
{ 0, 3 },
{ 1, 2 },
{ 1, 3 },
{ 2, 3 }
};
static void Autosprite2Deform( void ) {
int i, j, k;
int indexes;
float *xyz;
vec3_t forward;
if ( tess.numVertexes & 3 ) {
ri.Printf( PRINT_WARNING, "Autosprite2 shader %s had odd vertex count", tess.shader->name );
}
if ( tess.numIndexes != ( tess.numVertexes >> 2 ) * 6 ) {
ri.Printf( PRINT_WARNING, "Autosprite2 shader %s had odd index count", tess.shader->name );
}
if ( backEnd.currentEntity != &tr.worldEntity ) {
GlobalVectorToLocal( backEnd.viewParms.or.axis[0], forward );
} else {
VectorCopy( backEnd.viewParms.or.axis[0], forward );
}
// this is a lot of work for two triangles...
// we could precalculate a lot of it is an issue, but it would mess up
// the shader abstraction
for ( i = 0, indexes = 0 ; i < tess.numVertexes ; i+=4, indexes+=6 ) {
float lengths[2];
int nums[2];
vec3_t mid[2];
vec3_t major, minor;
float *v1, *v2;
// find the midpoint
xyz = tess.xyz[i];
// identify the two shortest edges
nums[0] = nums[1] = 0;
lengths[0] = lengths[1] = 999999;
for ( j = 0 ; j < 6 ; j++ ) {
float l;
vec3_t temp;
v1 = xyz + 4 * edgeVerts[j][0];
v2 = xyz + 4 * edgeVerts[j][1];
VectorSubtract( v1, v2, temp );
l = DotProduct( temp, temp );
if ( l < lengths[0] ) {
nums[1] = nums[0];
lengths[1] = lengths[0];
nums[0] = j;
lengths[0] = l;
} else if ( l < lengths[1] ) {
nums[1] = j;
lengths[1] = l;
}
}
for ( j = 0 ; j < 2 ; j++ ) {
v1 = xyz + 4 * edgeVerts[nums[j]][0];
v2 = xyz + 4 * edgeVerts[nums[j]][1];
mid[j][0] = 0.5f * (v1[0] + v2[0]);
mid[j][1] = 0.5f * (v1[1] + v2[1]);
mid[j][2] = 0.5f * (v1[2] + v2[2]);
}
// find the vector of the major axis
VectorSubtract( mid[1], mid[0], major );
// cross this with the view direction to get minor axis
CrossProduct( major, forward, minor );
VectorNormalize( minor );
// re-project the points
for ( j = 0 ; j < 2 ; j++ ) {
float l;
v1 = xyz + 4 * edgeVerts[nums[j]][0];
v2 = xyz + 4 * edgeVerts[nums[j]][1];
l = 0.5 * sqrt( lengths[j] );
// we need to see which direction this edge
// is used to determine direction of projection
for ( k = 0 ; k < 5 ; k++ ) {
if ( tess.indexes[ indexes + k ] == i + edgeVerts[nums[j]][0]
&& tess.indexes[ indexes + k + 1 ] == i + edgeVerts[nums[j]][1] ) {
break;
}
}
if ( k == 5 ) {
VectorMA( mid[j], l, minor, v1 );
VectorMA( mid[j], -l, minor, v2 );
} else {
VectorMA( mid[j], -l, minor, v1 );
VectorMA( mid[j], l, minor, v2 );
}
}
}
}
It’s from the tr_shade_calc.c file
