Gl ortho perspective rendering in gl tools.

Alexander Mitchell's picture

I am working on a project with go tools- specifically using gl ortho to render my scene without perspective.

I have done some research and discovered that gl ortho was originally included in open gl (as a direct call) for cad work.

Currently I have two questions: does gl ortho in gl tools use the open gl calls? And if so does this the. Render with the 3D processors of the graphics card?

I have a strange feeling that it renders with the 2D engine on my graphics card (a gtx670) which would also mean that the clock for that engine is very slow about 400 vs 1000.

I am needing to use the near gl setting to "cut into" a 3d object, and render without depth.

If there is a better and faster way let me know. And if indeed go ortho is using 3d or 2d for drawing.

Cheers Alex

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smokris's picture
Re: Gl ortho perspective rendering in gl tools.

The Kineme GL Ortho patch calls glOrtho() (as you can see in the source code).

I wouldn't expect that call to force using the software renderer — it merely adjusts the 3D vertex transformation matrix. However, the performance difference might be explained by pixel fill rate — if the geometry changes induced by glOrtho() cause more pixels to be shaded and overwritten, performance might drop.

Also, are you using Kineme GL Ortho inside an Iterator? If so, you might try moving it outside the Iterator. Quartz Composer is notoriously inefficient at executing patches inside Iterators, so every additional patch will degrade performance.