[Public WebGL] Possibility of not writing gl_Position is not addressed by WebGL spec

Olli Etuaho [email protected]
Tue Jun 18 08:53:22 PDT 2013

Hi all,

GLSL ES spec 1.0.17 section 10.13 says that not writing gl_Position results in undefined behavior, which is undesirable in WebGL. Current WebGL implementations do seem to enforce statically writing to gl_Position, but it's not mentioned in the WebGL spec. Should this be explicitly specified in the "Differences Between WebGL and OpenGL ES 2.0" section?

There's also a related problem in the conformance test glsl/literals/float_literal.vert.html, where vertex shader does not write gl_Position. I think the test should be fixed by adding writing to gl_Position.

A new test could also be written that specifically checks that not writing to gl_Position in a vertex shader will result in a shader compilation error.

Regards, Olli
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