OpenGL & GLSL: Greyscale texture not showing

Question

I'm trying to show a greyscale texture on the screen. I create my texture via

glGenTextures(1, &heightMap);
glBindTexture(GL_TEXTURE_2D, heightMap);
glTexImage2D(GL_TEXTURE_2D, 0, GL_R32F, 512, 512, 0, GL_RED, GL_FLOAT, colorData);

colorData is a float[512*512] with values between 0.0 and 1.0.

When rendering, I use:

glBindTexture(GL_TEXTURE_2D, heightMap);
glUniform1i(shader.GetUniformLocation("textureSampler"), 0);

shader.GetUniformLocation is a function of a library we use at university. It is essentially the same as glGetUniformLocation(shader, "textureSampler"), so don't be confused by it.

I render two triangles via triangle strip. My fragment shader is:

#version 330
layout(location = 0) out vec4 frag_color;
in vec2 texCoords;
uniform sampler2D textureSampler;

void main()
{
    frag_color = vec4(texture(textureSampler, texCoords).r, 0, 0, 1);
}

I know the triangles are rendered correctly (e.g. if I use vec4(1.0, 0, 0, 1) for frag_color, I get a completely red screen). However with the line above, I only get a completely black screen. Every texture value seems to be 0.0.

Does anyone have an idea, what I have done wrong? Are there mistakes in that few lines of code or are these completely correct and the error is somewhere else?

Answer 1

As one of the comments below says, setting glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); and glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); solves the problem. :)