CODEWITHSUNDEEP
c++opengl
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Nobody moving away from SE

Reputation: 9547

R32I sampler2D returns always 0

I have a (default vertex and) fragment shader that should resize textures and scale their color by a specific factor for brightness correction.

The result is rendered into an GL_UNSIGNED_INT_8_8_8_8 framebuffer.

#version 330

uniform sampler2D tex;
uniform vec2 screenSize;
uniform float scale;

layout(location = 0) out vec4 color;

void main()
{
    vec2 coord = gl_FragCoord.xy / screenSize;
    color = texture(tex, coord);
    color *= scale;
    color.a = 1;
}

When I bind a R32I texture to tex, the output from the texture call in the red channel is always 0, despite non 0 data being in the texture. I checked via apitrace that the correct texture is bound to tex and it contains values that go up to about 200. Normalizing this value should give an output of 9.3e-8 from texture(), while scale = 9.67e7.

There are no error messages (besides performance warnings) neither from glGetError nor from the debug callback.

What am I doing wrong? Is it forbidden to bind integer textures to (non integer) samplers?

Upvotes: 2

Views: 1198

Answers (1)

BDL
BDL

Reputation: 22167

Since you are using an integer format, you will have to use an isampler2D instead of your sampler.

So for samplers, floating-point samplers begin with "sampler​". Signed integer samplers begin with "isampler​", and unsigned integer samplers begin with "usampler​". If you attempt to read from a sampler where the texture's Image Format doesn't match the sampler's basic format (usampler2D with a GL_R8I, or sampler1D with GL_R8UI, for example), all reads will produce undefined values.

(Source: www.opengl.org)

Upvotes: 5

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