Heya....I was wondering if anyone could offer me some advice on speeding up some code which appears to be the major bottleneck in my program. Its the graphics drawing part, which I appreciate is going to be a bottleneck anyway, but if I''m doing something that might be a bit slow, I want to know....
Anyway - this function is called every frame:
int DrawGLScene(GLvoid) // Here''s Where We Do All The Drawing
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); // Clear The Screen And The Depth Buffer
glBindTexture(GL_TEXTURE_2D, texture[0]); // Select Our Texture
glLoadIdentity(); // Reset The View Before We Draw the particles
glTranslatef(0.0f,0.0f,zoom); // Zoom Into The Screen (Using The Value In ''zoom'')
glRotatef(rotate,0.0f,1.0f,0.0f); //rotate view
for (int i=0; i<pList.size(); i++) // Loop Through All The particles
{
glPushMatrix();
pList[i]->translate();
glRotatef(-rotate,0.0f,1.0f,0.0f); //rotate view back to facing screen - draw particles face on
pList[i]->drawParticle(particleDisplay);
glPopMatrix();
};
return TRUE; // Everything Went OK
}
OK - some explanation might be called for. Its a particle engine. pList is a vector of pointers to each particle object. Each frame, I reset the view matrix, zoom into the screen & rotate according to user set variables, then enter a loop that goes through each particle, translating to the particles location:
void particle::translate()
{
glTranslatef(loc.x,loc.y,loc.z);
};
then rotating backwards to billboard the particle, & drawing the particle:
void particle::drawParticle(GLuint& displayList)
{
if(lifespan > 5)
glColor4ub(r,g,b,255); //Draw at full color
else
glColor4ub(r,g,b,255*lifespan/5); //Fade out while dying
glCallList(displayList);
};
The top part sets the color, including a fade out as the particle nears the end of its life. Then I use a display list to draw the particle. The display list was defined in startup as
GLvoid BuildLists() // Build Box Display List
{
particleDisplay=glGenLists(1); // Building One List
glNewList(particleDisplay,GL_COMPILE); // New Compiled box Display List
glBegin(GL_TRIANGLE_STRIP); // Begin Drawing The Textured Quad
glTexCoord2f(1.0f, 1.0f); glVertex3f( 0.25f, 0.25f, 0.0f);
glTexCoord2f(0.0f, 1.0f); glVertex3f(-0.25f, 0.25f, 0.0f);
glTexCoord2f(1.0f, 0.0f); glVertex3f( 0.25f,-0.25f, 0.0f);
glTexCoord2f(0.0f, 0.0f); glVertex3f(-0.25f,-0.25f, 0.0f);
glEnd(); // Done Drawing The Textured Quad
glEndList();
};
Hmmm - that was a lot of code. So, assuming you''ve read this far - any hints? I was wondering if I could group those matrix translations & rotations into one operation, but can''t quite figure it out...
Cheers
Catfish
