CODEWITHSUNDEEP
opengl
Matias Morant
Matias Morant

Reputation: 513

glActiveTexture() throws GL_INVALID_ENUM

The line

glActiveTexture(GL_TEXTURE0+32);

throws GL_INVALID_ENUM (as I found running glGetError()), while

glActiveTexture(GL_TEXTURE0+31);

runs fine.

According to the documentation:

"GL_INVALID_ENUM is generated if texture is not one of GL_TEXTUREi, where i ranges from zero to the value of GL_MAX_COMBINED_TEXTURE_IMAGE_UNITS minus one."

but in my case GL_MAX_COMBINED_TEXTURE_IMAGE_UNITS is defined as 35661, and according to the same documentation

"The number of texture units is implementation dependent, but must be at least 80."

How could I solve this problem?

Just in case, GL_TEXTURE0 is defined as 33984 and my version of OpenGL is 2.1

Upvotes: 2

Views: 2473

Answers (2)

Jaa-c
Jaa-c

Reputation: 5157

GL_MAX_COMBINED_TEXTURE_IMAGE_UNITS may be defined as 35661, but that's not what you want, thats the value of an enum (same as GL_TEXTURE0 is defined as 33984). These values have no meaning at all.

You get the number by querying glGetIntegerv(GL_MAX_COMBINED_TEXTURE_IMAGE_UNITS, &texture_units);, which will return the number of textures you can use. It is very likely that it will be 32 on OpenGL 2.1 hw.

Upvotes: 5

datenwolf
datenwolf

Reputation: 162327

The documentation is a bit misleading. They mean the value retrieved by 

glGetIntegerv(GL_MAX_COMBINED_TEXTURE_IMAGE_UNITS, ...)

not the value of the token itself.

Upvotes: 4

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