Batch an openGL call to draw a lot of primitives

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Batch an openGL call to draw a lot of primitives

(4 posts) (3 voices)

Started 2 years ago by electronfish
Latest reply from UseCase

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electronfish
Member

Hello,

My game uses a lot of primitives, and I noticed this warning buried in the documentation..

"Warning:
These functions draws the Line, Point, Polygon, immediately. They aren't batched. If you are going to make a game that depends on these primitives, I suggest creating a batch."

I've googled, but can't find any information on creating a batch? There don't seem to be any classes in cocos2d. If anyone has any links to some code/documentation/tutorials, anything that would be useful I'd appreciate it.

Thank you.

Posted 2 years ago #
nsxdavid
Member

A batch just means that instead of drawing one line/point/polygon in a draw call, you do as many as possible.

When cocos2d draws sprites, it's drawing quads (aka two triangles) for each. And to do this fast with a lot of sprites, it provides the TextureAtlas class. This class is a perfect example of how to batch up a lot of primitives (triangles in this case) in an optimal way.

The functions you are looking at are mostly used for temporary rendering of things like debugging aids.

I use batch rendering extensively in geoDefense (which does not use cocos2d), and is the reason it can push so much stuff around the screen.

-- David

Posted 2 years ago #
electronfish
Member

Ok, I need to change the way I'm doing things then. Currently I'm using drawPoly to create a series of polygons of four points of varying height that line up and create a wave.

-(void) draw {
for (int i = 0; i < 60; i++) {

CGPoint vertices[] =
{ ccp((xspacing*i),-100),
ccp((xspacing*i),(yvalues[i])),
ccp((xspacing*(i+1)),-100),
ccp((xspacing*(i+1)),(yvalues[(i+1)])) };

// So this creates a tall box, with the top two points at slightly different heights.
// When all the boxes line up, they create a wave, basically a sine wave.

drawPoly( vertices, 4);

}

}

I'm guessing I need to create an array that contains all points, then draw that? Any tips on how I can collect all the points into an array? Thanks for the help again.

Posted 2 years ago #
UseCase
Member

Have you tried display lists or VBOs? You could create a CocosNode derived Class that encapsulates a display list or VBO.

Posted 2 years ago #

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