How do I get textures to work in OpenGL?

Question

I'm using the tutorials on http://arcsynthesis.org/gltut/ to learn OpenGL, it's required, I have to use it. Mostly I want to apply the textures from Tutorial 15 onto objects in tutorial 7 (world with UBO).

For now it seemed like the textures only work when mipmaps are turned on. This comes with a downside: The only mipmap used is the one with an index of zero, and that's the 1 colored 1x1 pixel one. I tried setting the minimum level of a mipmap higher or turning off mipmaps entirely, but even that doesn't fix thing, because then everything turns pitch black. Now I'll list the most important parts of my program

EDIT: I guess I'll add more details...

The vertex shader has something like this:

#version 330

layout(location = 0) in vec4 position;
layout(location = 1) in vec4 color;
layout(location = 2) in vec3 normal;
//Added these later 
layout(location = 5) in vec2 texCoord;
out vec2 colorCoord;

smooth out vec4 interpColor;
out vec3 vertexNormal;
out vec3 modelSpacePosition;
out vec3 cameraSpacePosition;

uniform mat4 worldToCameraMatrix;
uniform mat4 modelToWorldMatrix;
uniform mat3 normalModelToCameraMatrix;
uniform vec3 dirToLight;
uniform vec4 lightIntensity;
uniform vec4 ambientIntensity;
uniform vec4 baseColor;

uniform mat4 cameraToClipMatrix;

void main()
{
vertexNormal = normal;
vec3 normCamSpace = normalize(normalModelToCameraMatrix * vertexNormal);
cameraSpacePosition = normCamSpace;

float cosAngIncidence = dot(normCamSpace, dirToLight);
cosAngIncidence = clamp(cosAngIncidence, 0, 1);
modelSpacePosition.x = position.x;
modelSpacePosition.y = position.y;
modelSpacePosition.z = position.z;

vec4 temp = modelToWorldMatrix * position;
temp = worldToCameraMatrix * temp;
gl_Position = cameraToClipMatrix * temp;

interpColor = ((lightIntensity * cosAngIncidence) + (ambientIntensity)) * baseColor;
colorCoord= texCoord ;
}

The fragment shader like this:

#version 330
in vec3 vertexNormal;
in vec3 modelSpacePosition;

smooth in vec4 interpColor;

uniform vec3 modelSpaceLightPos;
uniform vec4 lightIntensity2;
uniform vec4 ambientIntensity2;

out vec4 outputColor;

//Added later
in vec2 colorCoord;
uniform sampler2D colorTexture;


void main()
{
vec3 lightDir2 = normalize(modelSpacePosition - modelSpaceLightPos);

float cosAngIncidence2 = dot(normalize(vertexNormal), lightDir2);
cosAngIncidence2 = clamp(cosAngIncidence2, 0,  1);

float light2DistanceSqr = dot(modelSpacePosition - modelSpaceLightPos, modelSpacePosition - modelSpaceLightPos);

//added
vec4 texture2 = texture(colorTexture, colorCoord);

outputColor = ((ambientIntensity2 + (interpColor*2))/4) + 
((((interpColor) * lightIntensity2/200 * cosAngIncidence2) + (ambientIntensity2* interpColor )) 
/( ( sqrt(light2DistanceSqr) + light2DistanceSqr)/200 ));
//No outputColor for texture testing
outputColor =  texture2 ; 

}
}

Those were both shaders. And here are the parts added to the .cpp:

#include 
#include "../framework/directories.h"     
[...]
const int g_colorTexUnit = 0;
GLuint g_checkerTexture = 0;

And here's the loader for the texture:

void LoadCheckerTexture()
{
try

{
std::string filename(LOCAL_FILE_DIR);
filename += "checker.dds";
std::auto_ptr
 pImageSet(glimg::loaders::dds::LoadFromFile(filename.c_str()));

glGenTextures(1, &g_checkerTexture);
glBindTexture(GL_TEXTURE_2D, g_checkerTexture);

glimg::SingleImage image = pImageSet->GetImage(0, 0, 0);
glimg::Dimensions dims = image.GetDimensions();
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB8, dims.width, dims.height, 0, GL_BGRA, GL_UNSIGNED_INT_8_8_8_8_REV, image.GetImageData());

glBindTexture(GL_TEXTURE_2D, 0);
}
catch(std::exception &e)
{
printf("%s
", e.what());
throw;
}
}

Naturally I've got this in void init():

LoadCheckerTexture();

And then when rendering the object:

glActiveTexture(GL_TEXTURE0 + g_colorTexUnit);
glBindTexture(GL_TEXTURE_2D,g_checkerTexture);
g_pLeftMesh->Render();
glBindSampler(g_colorTexUnit, 0);
glBindTexture(GL_TEXTURE_2D, 0);

With all of this, I get put pitch black for everything, however when I change the outputColor equation into "texture + outputColor;", everything looks normal. I have no idea what I'm doing wrong here. A friend tried to help me, we removed some unnecessairy stuff, but we got nothing running.

Jan Nowak · Accepted Answer

Ok guys, I've worked on this whole thing, and did manage to somehow get it running. First off I had to add samplers:

GLuint g_samplers;

//Add Later
void CreateSamplers()
{
glGenSamplers(1, &g_samplers);

    glSamplerParameteri(g_samplers, GL_TEXTURE_WRAP_S, GL_REPEAT);
    glSamplerParameteri(g_samplers, GL_TEXTURE_WRAP_T, GL_REPEAT);

//Linear mipmap Nearest
glSamplerParameteri(g_samplers, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glSamplerParameteri(g_samplers, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
}

I also added this to the file thing:

glimg::OpenGLPixelTransferParams xfer = glimg::GetUploadFormatType(pImageSet->GetFormat(), 0);

glimg::SingleImage image = pImageSet->GetImage(0, 0, 0);
glimg::Dimensions dims = image.GetDimensions();
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, dims.width, dims.height, 0, 
  xfer.format, xfer.type, image.GetImageData());

The xfer variable does get the format and type adjusted to the dds. Also the render code got turned into this:

//Added necessary 
glActiveTexture(GL_TEXTURE0 + g_colorTexUnit);
glBindTexture(GL_TEXTURE_2D,g_checkerTexture);
glBindSampler(g_colorTexUnit, g_samplers);
g_pLeftMesh->Render();
glBindSampler(g_colorTexUnit, 0);
glBindTexture(GL_TEXTURE_2D, 0);

And of course at the end of init() I needed to add the CreateSamplers thing:

//Added this later
LoadCheckerTexture();
CreateSamplers();

I'm sorry for all the trouble with all this, but guess OpenGL really is just this confusing and it was just dumb luck that I got it right. Just posting this so that people know

How do I get textures to work in OpenGL?

Answers (2)

Related Questions