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OpenGL I can't render depth to a texture. I need some help!

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So I've been trying to add shadows to my scene, and to achieve this I am trying to do the following:

 

Create a framebuffer object

Attach a texture to its depth attachment

Render my scene with the new framebuffer bound

Pass the depth texture as a uniform to my shader that draws to the screen's framebuffer

Sample the depth texture to determine if a fragment is in shadow

 

I have not been able to get this to work yet. The texture always returns 1.0 when it is sampled.

 

I also tried attaching a texture to the new framebuffer's color0 attachment, but that texture was all white too. I think there must be something wrong with my framebuffer, because I can't seem to get anything to render to it. Or maybe I am just accessing the textures attached to it incorrectly.

 

Every post I have found about the depth texture being white has said something about it not being linear, but I am using an orthographic projection so I believe it is linear. I also know that my transformation matrix for my shadow render is fine because when I use it to render my scene to the screen I get a nice orthographic view of my entire scene from the light direction.

 

I've spent about 10 hours trying to fix this, but I'm all out of ideas. I would really appreciate it if someone would look at my code and help me find what's wrong.

 

Here's my shader for rendering to the screen:

// vertex shader
const char* vertexSource =
    "#version 420\n"
    ""
    "in vec3 p;"
    "in vec3 n;"
    "out vec3 P;"
    "out vec3 N;"
    "out vec3 texCoord;"
    "out vec3 shadowCoord;"
    ""
    "uniform mat4 mvMatrix;"
    "uniform mat4 mvpMatrix;"
    "uniform mat4 normalMatrix;"
    "uniform mat4 shadowMatrix;"
    ""
    "void main() {"
    ""
    "   gl_Position = mvpMatrix * vec4(p,1.0);"
    "   vec4 p4 = mvMatrix * vec4(p,1.0);"
    "   P = p4.xyz / p4.w;"
    "   N = normalize((normalMatrix * vec4(n,1.0)).xyz);"
    ""
    "   float period = 0.001;"
    "   texCoord = p / period;"
    ""
    "   shadowCoord = (shadowMatrix * vec4(p, 1.0)).xyz;"
    "}";

// fragment shader
const char* fragmentSource =
    "#version 420\n"
    ""
    "in vec3 P;"
    "in vec3 N;"
    "in vec3 texCoord;"
    "in vec3 shadowCoord;"
    "uniform vec3 color;"
    "uniform vec3 specColor;"
    "uniform vec3 L;"
    "uniform sampler3D texNoise;"
    "uniform sampler2D texShadow;"
    ""
    "void main()"
    "{"
    "   float noise = texture(texNoise, texCoord).r;"
    "   float light_noise = (0.9 + 0.1 * noise);"
    ""
    "   float ambient = 0.4;"
    "   float diffuse = max(dot(N,L),0.0);"
    ""
    "   vec3 V = -normalize(P);"
    "   vec3 R = normalize(reflect(-L,N));"
    "   float specular = pow(max(dot(V,R),0.0),20);"
    "   float s = specular * specular;"
    "   specular = (1.0 - s) * specular * noise + s * specular;"
    ""
    "   vec3 sColor = 0.5 * (color + specColor);"
    ""
    "   if ( texture2D( texShadow, shadowCoord.xy ).r < shadowCoord.z );"
    "   {"
    "       specular *= 0.0;"
    "       diffuse *= 0.0;"
    "   }"
    ""
    "   vec3 final_color = color * (ambient + (0.2 + 0.4*(1.0-specular))*diffuse) * light_noise "
    "                    + color*specColor * (0.4*specular);"
    "   gl_FragColor = vec4(final_color,1.0);"
    "}";

Here's my shader for rendering depth to the texture:

const char* vertexSourceShadow =
    "#version 420\n"
    ""
    "in vec3 p;"
    "uniform mat4 mvpMatrix;"
    ""
    "void main() {"
    ""
    "   gl_Position = mvpMatrix * vec4( p, 1.0 );"
    "}";

// fragment shader
const char* fragmentSourceShadow =
    "#version 420\n"
    ""
    "void main()"
    "{"
    ""
    "}";

And here is my OpenGL code:

TerrainTile::TerrainTile(MeshData* md, Sun* sun)
{
    DEBUG = true;
    triangle_count = 0;

    this->sun = sun;

    // TRIANGLE SHADER ==================================================================

    // Create and compile the vertex shader
    vertexShader = glCreateShader(GL_VERTEX_SHADER);
    glShaderSource(vertexShader, 1, &vertexSource, NULL);
    glCompileShader(vertexShader);
    printShaderInfoLog(vertexShader);

    // Create and compile the fragment shader
    fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
    glShaderSource(fragmentShader, 1, &fragmentSource, NULL);
    glCompileShader(fragmentShader);
    printShaderInfoLog(fragmentShader);

    // Link the vertex and fragment shader into a shader program
    shaderProgram = glCreateProgram();
    glAttachShader(shaderProgram, vertexShader);
    glAttachShader(shaderProgram, fragmentShader);
    glLinkProgram(shaderProgram);
    //===================================================================================

    // LINE SHADER ======================================================================

    // Create and compile the vertex shader
    vertexShaderLine = glCreateShader(GL_VERTEX_SHADER);
    glShaderSource(vertexShaderLine, 1, &vertexSourceLine, NULL);
    glCompileShader(vertexShaderLine);
    printShaderInfoLog(vertexShaderLine);

    // Create and compile the fragment shader
    fragmentShaderLine = glCreateShader(GL_FRAGMENT_SHADER);
    glShaderSource(fragmentShaderLine, 1, &fragmentSourceLine, NULL);
    glCompileShader(fragmentShaderLine);
    printShaderInfoLog(fragmentShaderLine);

    // Link the vertex and fragment shader into a shader program
    shaderProgramLine = glCreateProgram();
    glAttachShader(shaderProgramLine, vertexShaderLine);
    glAttachShader(shaderProgramLine, fragmentShaderLine);
    glLinkProgram(shaderProgramLine);
    //===================================================================================

    // SHADOW SHADER ====================================================================

    // Create and compile the vertex shader
    vertexShaderShadow = glCreateShader(GL_VERTEX_SHADER);
    glShaderSource(vertexShaderShadow, 1, &vertexSourceShadow, NULL);
    glCompileShader(vertexShaderShadow);
    printShaderInfoLog(vertexShaderShadow);

    // Create and compile the fragment shader
    fragmentShaderShadow = glCreateShader(GL_FRAGMENT_SHADER);
    glShaderSource(fragmentShaderShadow, 1, &fragmentSourceShadow, NULL);
    glCompileShader(fragmentShaderShadow);
    printShaderInfoLog(fragmentShaderShadow);

    // Link the vertex and fragment shader into a shader program
    shaderProgramShadow = glCreateProgram();
    glAttachShader(shaderProgramShadow, vertexShaderShadow);
    glAttachShader(shaderProgramShadow, fragmentShaderShadow);
    glLinkProgram(shaderProgramShadow);
    //===================================================================================


    // create vertex array object
    glGenVertexArrays(1, &vao);
    
    // create vertex buffer
    glGenBuffers(1, &vbo);

    // create element buffer
    glGenBuffers(1, &ebo);


    // generate 3D texture --------------------------------------------------------------
    glGenTextures(1, &tex);
    glBindTexture(GL_TEXTURE_3D, tex);

    int tex_width = 256;
    int tex_height = 256;
    int tex_depth = 256;
    int tex_size = tex_width*tex_height*tex_depth;
    GLfloat* texture = new GLfloat[tex_size];
    for (int i = 0; i < tex_size; i++)
    {
        texture[i] = static_cast <GLfloat> (rand()) / static_cast <GLfloat> (RAND_MAX);
    }

    glTexImage3D(GL_TEXTURE_3D, 0, GL_RED, tex_width, tex_height, tex_depth, 0, GL_RED, GL_FLOAT, texture);
    delete [] texture;

    glTexParameteri(GL_TEXTURE_3D, GL_TEXTURE_WRAP_S, GL_REPEAT);
    glTexParameteri(GL_TEXTURE_3D, GL_TEXTURE_WRAP_T, GL_REPEAT);
    glTexParameteri(GL_TEXTURE_3D, GL_TEXTURE_WRAP_R, GL_REPEAT);
    glTexParameteri(GL_TEXTURE_3D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
    glTexParameteri(GL_TEXTURE_3D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);

    glActiveTexture(GL_TEXTURE0);
    glUniform1i(glGetUniformLocation(shaderProgram, "texNoise"), 0);
    //-----------------------------------------------------------------------------------

    // set state for shadows ------------------------------------------------------------
    
    glGenFramebuffers(1, &framebufferShadow);
    glBindFramebuffer(GL_FRAMEBUFFER, framebufferShadow);


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

    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_2D, GL_DEPTH_TEXTURE_MODE, GL_INTENSITY);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_COMPARE_MODE, GL_NONE);

    glTexImage2D(GL_TEXTURE_2D, 0, GL_DEPTH_COMPONENT, 1024, 1024, 0, GL_DEPTH_COMPONENT, GL_UNSIGNED_BYTE, NULL);
    
    glFramebufferTexture2D(GL_DRAW_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_TEXTURE_2D, depthTexture, 0);

    glDrawBuffer(GL_NONE);

    // check that our framebuffer is ok
    if (glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE)
        std::cout << "Shadow framebuffer is not complete.\n";
    else
        std::cout << "Shadow framebuffer is complete.\n";

    glBindFramebuffer(GL_FRAMEBUFFER, 0);
    //-----------------------------------------------------------------------------------

    update(md);

    if (DEBUG) debugInit();
}

TerrainTile::~TerrainTile()
{
    if (DEBUG) debugCleanUp();

    glDeleteTextures(1, &tex);
    glDeleteTextures(1, &depthTexture); 
    
    glDeleteShader(fragmentShader);
    glDeleteShader(vertexShader);
    glDeleteProgram(shaderProgram);   
    
    glDeleteShader(fragmentShaderLine);
    glDeleteShader(vertexShaderLine);
    glDeleteProgram(shaderProgramLine);

    glDeleteShader(fragmentShaderShadow);
    glDeleteShader(vertexShaderShadow);
    glDeleteProgram(shaderProgramShadow);

    glDeleteBuffers(1, &ebo);
    glDeleteBuffers(1, &vbo);
    glDeleteVertexArrays(1, &vao);

    glDeleteFramebuffers(1, &framebufferShadow);
}

void TerrainTile::draw(const View &view, bool lines, float dth)
{
    if (triangle_count > 0)
    {
        // draw the shadow map to the depth texture
        glm::mat4 shadowTransform = drawShadowMap(view.getPosition(), dth);
        
        if (DEBUG)
        {
            debugDraw();
        }

        // calculate transformation and set uniforms ----------------------------------------

        // model transform
        glm::mat4 model = glm::mat4(1.f);  

        // viewing transform    
        glm::mat4 viewing = glm::lookAt(view.getPosition(),
                                        view.getPosition() + view.getDirection(),
                                        view.getUp());

        // perspective transform
        glm::mat4 perspective = glm::perspective(view.getFOV(), view.getAspect(), 0.0001f, 5.0f);

        // final transformation
        glm::mat4 normalTransform = glm::lookAt(glm::vec3(0.0,0.0,0.0),
                                                view.getDirection(),
                                                view.getUp());
        glm::mat4 modelviewTransform = viewing * model;
        glm::mat4 mvpTransform = perspective * modelviewTransform;
        
        glm::vec4 lightDir4 = glm::vec4(sun->direction.x, sun->direction.y, sun->direction.z, 1.0);
        lightDir4 = normalTransform * lightDir4;
        glm::vec3 lightDir3 = glm::normalize(glm::vec3(lightDir4));

        glm::mat4 bias = glm::mat4(0.5, 0.0, 0.0, 0.0,
                                   0.0, 0.5, 0.0, 0.0,
                                   0.0, 0.0, 0.5, 0.0,
                                   0.5, 0.5, 0.5, 1.0);
        glm::mat4 shadowBiasTransform = bias * shadowTransform;
        //-----------------------------------------------------------------------------------

        // draw fill ------------------------------------------------------------------------
        glBindVertexArray(vao);

        glUseProgram(shaderProgram);

        // Specify the layout of the vertex data
        GLint positionAttribute = glGetAttribLocation(shaderProgram, "p");
        glEnableVertexAttribArray(positionAttribute);
        glVertexAttribPointer(positionAttribute, 3, GL_FLOAT, GL_FALSE, 6*sizeof(float), 0);

        GLint normalAttribute = glGetAttribLocation(shaderProgram, "n");
        glEnableVertexAttribArray(normalAttribute);
        glVertexAttribPointer(normalAttribute, 3, GL_FLOAT, GL_FALSE, 6*sizeof(float), (void*)(3*sizeof(float)));

        glActiveTexture(GL_TEXTURE0);
        glBindTexture(GL_TEXTURE_3D, tex);
        glUniform1i(glGetUniformLocation(shaderProgram, "texNoise"), 0);

        glActiveTexture(GL_TEXTURE1);
        glBindTexture(GL_TEXTURE_2D, depthTexture);
        glUniform1i(glGetUniformLocation(shaderProgram, "texShadow"), 1);

        // get uniform locations from shaders
        GLint color_uniform_tri = glGetUniformLocation(shaderProgram, "color");
        GLint scolor_uniform_tri = glGetUniformLocation(shaderProgram, "specColor");
        GLint light_uniform_tri = glGetUniformLocation(shaderProgram, "L");
        GLint modelview_uniform_tri = glGetUniformLocation(shaderProgram, "mvMatrix");
        GLint transform_uniform_tri = glGetUniformLocation(shaderProgram, "mvpMatrix");
        GLint normal_uniform_tri = glGetUniformLocation(shaderProgram, "normalMatrix");
        GLint shadow_uniform_tri = glGetUniformLocation(shaderProgram, "shadowMatrix");

        glm::vec3 color = glm::vec3(237/255.f,201/255.f,175/255.f);
        glUniform3fv(color_uniform_tri, 1, glm::value_ptr(color));
        glUniform3fv(scolor_uniform_tri, 1, glm::value_ptr(sun->color));
        glUniform3fv(light_uniform_tri, 1, glm::value_ptr(lightDir3));
        glUniformMatrix4fv(modelview_uniform_tri, 1, GL_FALSE, glm::value_ptr(modelviewTransform));
        glUniformMatrix4fv(transform_uniform_tri, 1, GL_FALSE, glm::value_ptr(mvpTransform));
        glUniformMatrix4fv(normal_uniform_tri, 1, GL_FALSE, glm::value_ptr(normalTransform));
        glUniformMatrix4fv(shadow_uniform_tri, 1, GL_FALSE, glm::value_ptr(shadowBiasTransform));



        glPolygonOffset(1,1);
        glEnable(GL_POLYGON_OFFSET_FILL);
        glDrawElements(GL_TRIANGLES, triangle_count * 3, GL_UNSIGNED_INT, 0);
        glDisable(GL_POLYGON_OFFSET_FILL);
        //-----------------------------------------------------------------------------------

        // draw outline ---------------------------------------------------------------------
        if (lines)
        {
            glUseProgram(shaderProgramLine);

            // Specify the layout of the vertex data
            GLint positionAttributeLine = glGetAttribLocation(shaderProgramLine, "p");
            glEnableVertexAttribArray(positionAttributeLine);
            glVertexAttribPointer(positionAttributeLine, 3, GL_FLOAT, GL_FALSE, 6*sizeof(float), 0);

            // get uniform locations from shaders
            GLint color_uniform_line = glGetUniformLocation(shaderProgramLine, "color");
            GLint transform_uniform_line = glGetUniformLocation(shaderProgramLine, "mvpMatrix");

            color = glm::vec3(0.f,0.f,0.f);
            glUniform3fv(color_uniform_line, 1, glm::value_ptr(color));
            glUniformMatrix4fv(transform_uniform_line, 1, GL_FALSE, glm::value_ptr(mvpTransform));

            glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
            glDrawElements(GL_TRIANGLES, triangle_count * 3, GL_UNSIGNED_INT, 0);
            glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
        }
        //-----------------------------------------------------------------------------------

        //===================================================================================
        
        // make sure VAO is not changed from the outside
        glBindVertexArray(0);
    }
}

glm::mat4 TerrainTile::drawShadowMap(glm::vec3 pos, float dth)
{
    glBindFramebuffer(GL_FRAMEBUFFER, framebufferShadow);
    glClear(GL_DEPTH_BUFFER_BIT);
    glDisable(GL_CULL_FACE);

    // calculate transformation
    glm::mat4 shadowPerspective = glm::ortho<float>(-dth,dth,-dth,dth,-dth,dth);
    glm::vec3 shadowPoint = glm::normalize(pos);
    glm::mat4 shadowViewing = glm::lookAt(shadowPoint,
                                          shadowPoint - sun->direction,
                                          shadowPoint);
    glm::mat4 shadowModel = glm::mat4(1.f);
    glm::mat4 shadowTransform = shadowPerspective * shadowViewing * shadowModel;

    glUseProgram(shaderProgramShadow);

    GLint shadow_transform_uniform = glGetUniformLocation(shaderProgramShadow, "mvpMatrix");
    glUniformMatrix4fv(shadow_transform_uniform, 1, GL_FALSE, glm::value_ptr(shadowTransform));

    glBindVertexArray(vao);

    // Specify the layout of the vertex data
    GLint positionAttribute = glGetAttribLocation(shaderProgramShadow, "p");
    glEnableVertexAttribArray(positionAttribute);
    glVertexAttribPointer(positionAttribute, 3, GL_FLOAT, GL_FALSE, 6*sizeof(float), 0);

    
    glDrawElements(GL_TRIANGLES, triangle_count * 3, GL_UNSIGNED_INT, 0);


    // change back
    glEnable(GL_CULL_FACE);
    glBindVertexArray(0);
    glBindFramebuffer(GL_FRAMEBUFFER, 0);

    return shadowTransform;
}

void TerrainTile::update(MeshData* md)
{
    if (md != NULL)
    {
        // get vertices and triangles
        float* vertices = md->vertices;
        int vertex_count = md->vertex_count;

        int* triangles = md->triangles;
        triangle_count = md->triangle_count;

        glBindVertexArray(vao);

        glBindBuffer(GL_ARRAY_BUFFER, vbo);
        glBufferData(GL_ARRAY_BUFFER, sizeof(float) * vertex_count * 6, vertices, GL_DYNAMIC_DRAW);

        glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ebo);
        glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(GLuint) * triangle_count * 3, triangles, GL_DYNAMIC_DRAW);
        
        // make sure VAO is not changed from the outside
        glBindVertexArray(0);
    }
}

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Your depth fragment shader does nothing?  I mean, I suppose this could work but just to be safe I'd write out some color

 

Also assure your glDepthMask is GL_TRUE ?

 

Try using GL_FRAMEBUFFER as the first param to glFramebufferTexture2D

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Your depth fragment shader does nothing?  I mean, I suppose this could work but just to be safe I'd write out some color

 

Also assure your glDepthMask is GL_TRUE ?

 

Try using GL_FRAMEBUFFER as the first param to glFramebufferTexture2D

Writing a color didn't make a difference. glDepthMask is True. Changing GL_DRAW_FRAMEBUFFER to GL_FRAMEBUFFER doesn't make a difference either.

 

I decided to delete all of my shadow code and start over. I'm getting values in my depth texture now, but other weird things are happening. I have the texture displayed on the top right corner of the screen and it looks right, but the shadows are definitely not correct in the final render. Resizing the window has a large effect on the shadows which is really confusing. At least now I have something to work with.

 

Thanks for taking the time to look over my code. I appreciate it!

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I just figured out what was wrong. I wasn't calling glViewport before rendering to my offscreen framebuffer, so it was using the wrong size for rendering. Now the shadows are working! I removed a lot of other features when I started over with shadows, so I still have some work to do to get everything working together.

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      EDIT: Depth texture attachment:
      glTexImage2D(GL_TEXTURE_2D, 0,GL_DEPTH_COMPONENT24,fbo->width,fbo->height,0,GL_DEPTH_COMPONENT,GL_FLOAT,NULL); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE); glFramebufferTexture2D(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_TEXTURE_2D, fbo->depthTexture, 0);
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