Shader: determine if camera is orthographic

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Does anyone know of a way to determine from within a shader whether the camera currently rendering it is orthographic?

There are a number of camera parameters that can be accessed, but it looks like the ortho status, or other information that could be used to determine it like the field of view, is not among them:

http://docs.unity3d.com/Documentation/Components/SL-BuiltinValues.html

My particular use case is this: I've written code to do billboarding, and it bases the size of the billboard on the camera distance so it always appears as the same pixel size. Obviously, you don't want to do this with ortho cameras, as size doesn't change with distance from the camera.

I could do it with a shader variable, but that doesn't work if I'm rendering with multiple cameras simultaneously. I could do it with shader replacement, but that requires keeping two shaders synced with each other - not ideal.

Answer 1

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Answer by Jessy · Jun 17, 2013 at 06:15 PM

The values that matter are in UNITY_MATRIX_P[3].zw. UNITY_MATRIX_P[3][3] will give you a zero for perspective and one for ortho, for example.

http://www.songho.ca/opengl/gl_projectionmatrix.html

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Julien-Lynge · Jun 17, 2013 at 07:04 PM 1

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Thank you, Jessy!

I was able to integrate that seamlessly into the shader as a multiplier, and it seems to be working perfectly.

I wish my group would actually give me time to study up on shaders - there's so much to know :) At the very least I'll read through your link after work.

Answer 2

Answer by Acegikmo · Apr 28, 2020 at 03:29 PM

a slightly more straightforward value,

unity_OrthoParams.w

0 when your camera is perspective

1 when your camera is ortho

also, when orthographic, x = width, y = height (z is unused)

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Shader: determine if camera is orthographic

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