CODEWITHSUNDEEP
opengl
Irbis
Irbis

Reputation: 1491

glTexImage2D null data pointer and memory initialization

Let's assume that 2D texture is defined using glTexImage2D with the null data pointer. Does passing the null data pointer zeroes memory or I may get some garbage data when a fragment shader samples that texture ?

vec3 color = texture(texture0, texCoord).xyz;

Upvotes: 2

Views: 415

Answers (1)

Yakov Galka
Yakov Galka

Reputation: 72449

The documentation clearly states:

data may be a null pointer. In this case, texture memory is allocated to accommodate a texture of width width and height height. ... The image is undefined if the user tries to apply an uninitialized portion of the texture image to a primitive.

So yes -- you will get garbage. Keep in mind that zeroes are also valid garbage, so don't use that as a proof that it "works".

The easiest way to clear a texture to all-zeros is with glClearTexImage:

glClearTexImage(texture, 0, GL_RGBA, GL_UNSIGNED_BYTE, 0);

For this function data == 0 actually means "all zeroes".

Upvotes: 2

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