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 <glimg/glimg.h>
#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<glimg::ImageSet>
 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\n", 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.

Answer 1

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

Answer 2

Your fail to add textures may be caused by:

• Have you add texture coordinates to objects? (this is the most probable cause, because you are adding textures to non textured tutorial), add textures to VAO.
• Did you add uniform textureunit (Sampler2D)? (it must be uniform, else texturing will not work properly)
• Is your texture loaded,binded,enabled (GL_TEXTURE_2D) ?
• Is your active texture unit - 0? if not change layout/multitexture coords or set active texture 0

This two codes are simple texturing shaders (texture unit 0) no special things (like light,blend,bump,...):

tm_l2g is transformation local obj space -> world space (Modelview)
tm_g2s is transformation world space -> screen space (Projection)
pos are vertex coordinates
txt are texture coordinates
col are colors

Do not forget to change uniform names and layout locations to yours.

Vertex:

//------------------------------------------------------------------
#version 420 core
//------------------------------------------------------------------
uniform mat4x4 tm_l2g;
uniform mat4x4 tm_g2s;

layout(location=0) in vec3 pos;
layout(location=1) in vec4 col;
layout(location=2) in vec2 txr;

out smooth vec4 pixel_col;
out smooth vec2 pixel_txr;
//------------------------------------------------------------------
void main(void)
    {
    vec4 p;
    p.xyz=pos;
    p.w=1.0;
    p=tm_l2g*p;
    p=tm_g2s*p;
    gl_Position=p;
    pixel_col=col;
    pixel_txr=txr;
    }
//------------------------------------------------------------------

fragment:

//------------------------------------------------------------------
#version 420 core
//------------------------------------------------------------------
in smooth vec4 pixel_col;
in smooth vec2 pixel_txr;
uniform sampler2D   txr_texture0;
out layout(location=0) vec4 frag_col;
//------------------------------------------------------------------
void main(void)
    {
    vec4 col;
    col=texture(txr_texture0,pixel_txr.st);
    frag_col=col*pixel_col;
    }
//------------------------------------------------------------------

[edit1] CPU old style OpenGL render code (initializations are not included its only render code they can be found here)

//------------------------------------------------------------------
// set modelview,projection,textures,bind GLSL programs...
GLfloat a=10.0,z=0.0;
glColor3f(1.0,1.0,1.0);
glBegin(GL_QUADS);
// textured quad
glTexCoord2f(0.0,0.0); glVertex3f(-a,-a,z);
glTexCoord2f(0.0,1.0); glVertex3f(-a,+a,z);
glTexCoord2f(1.0,1.0); glVertex3f(+a,+a,z);
glTexCoord2f(1.0,0.0); glVertex3f(+a,-a,z);
// reverse order quad to be shore that at least one passes by CULL_FACE
glTexCoord2f(1.0,0.0); glVertex3f(+a,-a,z);
glTexCoord2f(1.0,1.0); glVertex3f(+a,+a,z);
glTexCoord2f(0.0,1.0); glVertex3f(-a,+a,z);
glTexCoord2f(0.0,0.0); glVertex3f(-a,-a,z);
glEnd();

//------------------------------------------------------------------

[edit2] ok here goes VAO/VBO render code,...

//------------------------------------------------------------------------------
// enum of VBO locations (it is also your layout location) I use enums for simple in code changes
enum _vbo_enum
    {
    _vbo_pos=0,     // glVertex
    _vbo_col,       // glColor
    _vbo_tan,       // glNormal
    _vbo_unused0,   // unused (at least i dont see anything at this location in your code)
    _vbo_unused1,   // unused (at least i dont see anything at this location in your code)
    _vbo_txr,       // glTexCoord
    _vbos
    };
//------------------------------------------------------------------------------
// 'global' names and size for OpenGL mesh in VAO/VBO ... similar ot texture names/handles
GLuint vao[1],vbo[_vbos],num_pnt=0;
//------------------------------------------------------------------------------
void VAO_init_cube()    // call this before VAO use,...but after OpenGL init !
    {
    //[1] first you need some model to render (mesh), here is a simple cube
    // size,position of cube - change it that it is visible in your scene
    const GLfloat a=1.0,x=0.0,y=0.0,z=0.0;
    // cube points 3f x,y,z
    GLfloat mesh_pos[]=
        {
        x-a,y-a,z-a,x-a,y+a,z-a,x+a,y+a,z-a,x+a,y-a,z-a,
        x-a,y-a,z+a,x-a,y+a,z+a,x+a,y+a,z+a,x+a,y-a,z+a,
        x-a,y-a,z-a,x-a,y-a,z+a,x+a,y-a,z+a,x+a,y-a,z-a,
        x-a,y+a,z-a,x-a,y+a,z+a,x+a,y+a,z+a,x+a,y+a,z-a,
        x-a,y-a,z-a,x-a,y+a,z-a,x-a,y+a,z+a,x-a,y-a,z+a,
        x+a,y-a,z-a,x+a,y+a,z-a,x+a,y+a,z+a,x+a,y-a,z+a,
        };
    // cube colors 3f r,g,b
    GLfloat mesh_col[]=
        {
        0.0,0.0,0.0,0.0,1.0,0.0,1.0,1.0,0.0,1.0,0.0,0.0,
        0.0,0.0,1.0,0.0,1.0,1.0,1.0,1.0,1.0,1.0,0.0,1.0,
        0.0,0.0,0.0,0.0,0.0,1.0,1.0,0.0,1.0,1.0,0.0,0.0,
        0.0,1.0,0.0,0.0,1.0,1.0,1.0,1.0,1.0,1.0,1.0,0.0,
        0.0,0.0,0.0,0.0,1.0,0.0,0.0,1.0,1.0,0.0,0.0,1.0,
        1.0,0.0,0.0,1.0,1.0,0.0,1.0,1.0,1.0,1.0,0.0,1.0,
        };
    // cube normals 3f x,y,z
    GLfloat mesh_tan[]=
        {
        -0.6,-0.6,-0.6,-0.6,+0.6,-0.6,+0.6,+0.6,-0.6,+0.6,-0.6,-0.6,
        -0.6,-0.6,+0.6,-0.6,+0.6,+0.6,+0.6,+0.6,+0.6,+0.6,-0.6,+0.6,
        -0.6,-0.6,-0.6,-0.6,-0.6,+0.6,+0.6,-0.6,+0.6,+0.6,-0.6,-0.6,
        -0.6,+0.6,-0.6,-0.6,+0.6,+0.6,+0.6,+0.6,+0.6,+0.6,+0.6,-0.6,
        -0.6,-0.6,-0.6,-0.6,+0.6,-0.6,-0.6,+0.6,+0.6,-0.6,-0.6,+0.6,
        +0.6,-0.6,-0.6,+0.6,+0.6,-0.6,+0.6,+0.6,+0.6,+0.6,-0.6,+0.6,
        };
    // cube texture coords 2f s,t
    GLfloat mesh_txr[]=
        {
        0.0,0.0,0.0,1.0,1.0,1.0,1.0,0.0,
        0.0,0.0,0.0,1.0,1.0,1.0,1.0,0.0,
        0.0,0.0,0.0,1.0,1.0,1.0,1.0,0.0,
        0.0,0.0,0.0,1.0,1.0,1.0,1.0,0.0,
        0.0,0.0,0.0,1.0,1.0,1.0,1.0,0.0,
        0.0,0.0,0.0,1.0,1.0,1.0,1.0,0.0,
        };
    // init VAO/VBO
    glGenVertexArrays(1,vao);   // allocate 1 x VAO
    glGenBuffers(_vbos,vbo);    // allocate _vbos x VBO
    // copy mesh to VAO/VBO ... after this you do not need the mesh anymore
    GLint i,sz,n;               // n = number of numbers per 1 entry
    glBindVertexArray(vao[0]);
    num_pnt=sizeof(mesh_pos)/(sizeof(GLfloat)*3);   // num of all points in mesh

    i=_OpenGLVAOgfx_pos; n=3; sz=sizeof(GLfloat)*n;
    glBindBuffer(GL_ARRAY_BUFFER,vbo[i]);
    glBufferData(GL_ARRAY_BUFFER,sz*num_pnt,mesh_pos,GL_STATIC_DRAW);
    glEnableVertexAttribArray(i);
    glVertexAttribPointer(i,n,GL_FLOAT,GL_FALSE,0,0);

    i=_OpenGLVAOgfx_col; n=3; sz=sizeof(GLfloat)*n;
    glBindBuffer(GL_ARRAY_BUFFER,vbo[i]);
    glBufferData(GL_ARRAY_BUFFER,sz*num_pnt,mesh_col,GL_STATIC_DRAW);
    glEnableVertexAttribArray(i);
    glVertexAttribPointer(i,n,GL_FLOAT,GL_FALSE,0,0);

    i=_OpenGLVAOgfx_tan; n=3; sz=sizeof(GLfloat)*n;
    glBindBuffer(GL_ARRAY_BUFFER,vbo[i]);
    glBufferData(GL_ARRAY_BUFFER,sz*num_pnt,mesh_tan,GL_STATIC_DRAW);
    glEnableVertexAttribArray(i);
    glVertexAttribPointer(i,n,GL_FLOAT,GL_FALSE,0,0);

    i=_OpenGLVAOgfx_txr; n=2; sz=sizeof(GLfloat)*n;
    glBindBuffer(GL_ARRAY_BUFFER,vbo[i]);
    glBufferData(GL_ARRAY_BUFFER,sz*num_pnt,mesh_txr,GL_STATIC_DRAW);
    glEnableVertexAttribArray(i);
    glVertexAttribPointer(i,n,GL_FLOAT,GL_FALSE,0,0);

    glBindVertexArray(0);
    }
//------------------------------------------------------------------------------
void VAO_draw() // call this to draw your mesh,... need to enable and bind textures,...  before use
    {
    glDisable(GL_CULL_FACE);
    glEnable(GL_DEPTH_TEST);
    glDepthFunc(GL_LEQUAL);

    glBindVertexArray(vao[0]);
     glEnableVertexAttribArray(_vbo_pos);
     glEnableVertexAttribArray(_vbo_col);
     glEnableVertexAttribArray(_vbo_tan);
    glDisableVertexAttribArray(_vbo_unused0);
     glEnableVertexAttribArray(_vbo_txr);

    glDrawArrays(GL_QUADS,0,num_pnt);

    glDisableVertexAttribArray(_vbo_pos);
    glDisableVertexAttribArray(_vbo_col);
    glDisableVertexAttribArray(_vbo_tan);
    glDisableVertexAttribArray(_vbo_unused0);
    glDisableVertexAttribArray(_vbo_unused1);
    glDisableVertexAttribArray(_vbo_txr);
    glBindVertexArray(0);
    }
//------------------------------------------------------------------------------
void VAO_exit() // clean up ... call this when you do not need VAO/VBO anymore
    {
    glDisableVertexAttribArray(_vbo_pos);
    glDisableVertexAttribArray(_vbo_col);
    glDisableVertexAttribArray(_vbo_tan);
    glDisableVertexAttribArray(_vbo_unused0);
    glDisableVertexAttribArray(_vbo_unused1);
    glDisableVertexAttribArray(_vbo_txr);
    glBindVertexArray(0);
    glDeleteVertexArrays(1,vao);
    glDeleteBuffers(_vbos,vbo);
    }
//------------------------------------------------------------------------------

[edit3] if you are win32/64 user you can try my IDE for GLSL

It is very simple and easy to use, but cannot change texture/attrib locations. Press [F1] for help,... [F9] for run [F10] for return to normal OpenGL mode. Also txt-editor is little buggy sometimes but it is enough for my purpose.

• GLSL IDE