Using OpenGL commands to write to buffers

[Pixel Perfect]

I've seen code in the past (from Masterxilo I seem to recollect) which allowed the use of openGL commands to write to 2D and 3D space but from recollection this appeared to be writing to the backbuffer and normally took place after all the Leadwerks rendering had taken place. Is it possible to write to any buffer using openGLcommands?

 

What I'm looking to do ideally is write a texture created in memory to the background world and create a series of textured triangles to be rendered over it at this stage. Basically integrate in an already existing openGL sky rendering system. So I need access to Leadwerks framewerk buffers via openGL.

 

Any advice/help would be appreciated.

[Flexman]

Are you using any kind of framework that handles drawing to the back-buffer? If so, then you can probably locate the part of the code where it clears the back-buffer and insert a call to your own openGL functions.

 

Using SetBuffer() will work for openGL commands, you might need to do a bit of housekeeping, like inserting

 

SetBuffer(outputBufferMadeWithLE) ;
glDisable(GL_BLEND); // OR SetBlend(0);
glPushMatrix() ;
glOrtho(0, 512, 512, 0, 1, 10); // set for a 512x512 buffer
glMatrixMode(GL_PROJECTION) ;
glLoadIdentity();

CallMySkyCodeHere();

glPopMatrix();

 

So there shouldn't be much to do. It can get a little upset if you change OpenGL states and don't put them back the way LE is expecting. So you might want to bookend your custom part with the state push/pop commands.

 

Other than that you should be fine to do what you want to do.

[Pixel Perfect]

Are you using any kind of framework that handles drawing to the back-buffer?

Yes, I'm using a slightly modified version of the original C++ Framewerk code.

 

 

 

Using SetBuffer() will work for openGL commands, you might need to do a bit of housekeeping

Excellent, that's really good news. Thanks for your advice, I'll have a play with this.

[Masterxilo]

Yeah you can render to any buffer just fine with the opengl commands.