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OpenGL Deferred rendering shader spaces issue

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Hello,
 
I have currently got into shaders again. Now, I want some clarification.
 
As I have been googling, reading and all I have come to conclusion about spaces:
 
Origin is just something you define, like (0,1,0), it's a position from the Model's center or OpenGL coordinate center.
Model transform(M) is the so told model center's transform regarding the OpenGL coordinate center. (M*vec)
View transform(V) is the Model's transform according to camera, as the camera doesn't move and is at the (0,0,0). (V*M*vec)
Projection(P) is what projects the View to Screen. (P*V*M*vec)
(Please correct me if I am wrong.)
 
So now to the problem:
 
I am trying to implement a Deferred Rendering G-Buffer.
I have got a FBO with all the required textures: Diffuse, Depth, Normals, Position, UV(I am not using UVs in my particular sample).
The main issue starts here. I know that Diffuse and Depth are okay Out of the Box.
I need Normals and Positions in View-Space, for my SSAO implementation. I get that by multiplying normals I have calculated in my Geometry shader by Transpose Inverse View*Model matrix and packing them.
 
But how do I need to calculate Positions texture?
Also, are there any clarifications what exactly are: Model-Space, View-Space, Camera-Space? Are they exactly as I told?
 
This is my G-Buffer Shader Set:
 
Vertex:
#version 330
// THE FOOD CHAIN GOES LIKE THIS
// Vert
// Geom
// Frag
 
layout (location=0) in vec3 pos;
layout (location=6) in vec4 col;
 
uniform mat4 M;
uniform mat4 V;
uniform mat4 P;
 
out vData
{
    vec4 color;
vec4 pos;
}vertex;
 
void main()
{
vec4 _col=vec4(col.x/255,col.y/255,col.z/255,col.w/255);
mat4 MVP = P*V*M;
vertex.color=_col;
vertex.pos=vec4(pos,1.0);
gl_Position = MVP * vec4(pos,1);
}
 
Geometry
#version 330
// THE FOOD CHAIN GOES LIKE THIS
// Vert
// Geom
// Frag
 
layout (triangles) in;
layout (triangle_strip, max_vertices=3) out;
 
uniform mat3 normMatrix;
uniform mat4 M;
uniform mat4 V;
uniform mat4 P;
 
 
in vData
{
    vec4 color;
vec4 pos;
}vertex[];
 
out vec3 normal;
out vec4 color;
out vec4 position;
 
void main()
{
vec3 calcNorm=normalize(normMatrix*cross(vertex[1].pos.xyz - vertex[0].pos.xyz, vertex[2].pos.xyz - vertex[0].pos.xyz))*0.5+0.5;
normal = calcNorm;
color = vertex[0].color;
position = M*vertex[0].pos;
    gl_Position = gl_in[0].gl_Position;
    EmitVertex();
normal = calcNorm;
color = vertex[1].color;
position = M*vertex[1].pos;
    gl_Position = gl_in[1].gl_Position;
    EmitVertex();
normal = calcNorm;
color = vertex[2].color;
position = M*vertex[2].pos;
    gl_Position = gl_in[2].gl_Position;
    EmitVertex();
    EndPrimitive();
}
 
Fragment
#version 330
// THE FOOD CHAIN GOES LIKE THIS
// Vert
// Geom
// Frag
 
in vec4 position;
in vec3 normal;
in vec4 color;
 
layout (location = 0) out vec3 Gdiffuse;
layout (location = 1) out vec3 Gnormal;
layout (location = 2) out vec3 Gposition;
layout (location = 3) out vec3 Gtexcoord;
 
void main(){
 
Gdiffuse = color.rgb;
Gnormal = normal;
Gposition = position.rgb;
Gtexcoord = vec3(0);
}
 
This is how it looks:
48811a409e.png
(Upper left - diffuse, Lower left - random normals for SSAO, Right - Depth, Normal, Position, UV)
 
( Yeah, it's a voxel engine, generic. tongue.png But it's really fun learning to optimize and all. smile.png Nothing more satisfying than to see it be faster and more memory efficient. smile.png )
 

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Also, are there any clarifications what exactly are: Model-Space, View-Space, Camera-Space? Are they exactly as I told?

Model space or object space, is the space in which your mesh is defined. When you load your mesh, each vertex is in model/object space.

Eye,view or camera space , is the space around wink.png  your camera, with the camera position (center of projection) being the center (0,0,0).

 

The common transformation is

objectspace ==model-transform==> wordspace ==view transform==> viewspace ==projection transform ==> screenspace

 

When using deferred rendering, the g-buffer is typically in view/camera space.

 

 

 

 


But how do I need to calculate Positions texture?

If you are in camera-space, you only need to save the depth, that is all. You dont need the position, because you can reconstruct the camera-space position from the screen-pixel position (aka fragment position) which is available in the fragment/pixel shader and the depth (there are different approaches to do it, best to use the search function/google for more detailed informations).

Edited by Ashaman73

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Wow, that was fast. :)

Thank you very much for getting me on track and clarifying!

 

(Also, saw a very neat trick for alpha you got there! Will definitely try it. :) )

 

Thanks! Will see how it goes, if I struggle anymore or not.

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vec4 _col=vec4(col.x/255,col.y/255,col.z/255,col.w/255);

 

you can just write col.xyzw / 255.0 here, or col / 255.0. 255 is an integer though and might not compile on stricter implementations (im not actually sure)

 

vec3 calcNorm=normalize(normMatrix*cross(vertex[1].pos.xyz - vertex[0].pos.xyz, vertex[2].pos.xyz - vertex[0].pos.xyz)) * 0.5 + 0.5;

 

is invalid and will likely not compile on stricter implementations, it should be + vec3(0.5);

Edited by Kaptein

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Thank you for your responses. smile.png I have fixed my normals and positions calculations accordingly and now, I presume, they are both in ModelView space, which is required for the implementation of this SSAO approach. This is how my buffers and SSAO look now:

 

fcda583769.png

 

I had to convert the SSAO code from what I think is DirectX shading language to GLSL, so there might be some mistakes by me. What I could be doing wrong, to get such distorted 4-piece screen results? This is my SSAO conversion:

 

Vertex Shader

#version 330
layout (location=0) in vec3 pos;
layout (location=1) in vec2 tex;

out vec4 _pos;
out vec2 _uv;

void main(void)
{
	_pos = vec4(pos,1);
    _uv = tex;
    gl_Position = vec4(pos,1);
}

Fragment shader

#version 330

uniform sampler2D g_buffer_diff;
uniform sampler2D g_buffer_norm;
uniform sampler2D g_buffer_pos;
uniform sampler2D g_random;
uniform sampler2D g_depth;

const float g_screen_size=1280*768;
const float random_size=64*64;
const float g_sample_rad=0.006;
const float g_intensity=1.38;
const float g_scale=0.000002;
const float g_bias=0.07;

in vec4 _pos;
in vec2 _uv;

out vec4 fragColor;

vec3 getPosition(vec2 uv)
{
return texture2D(g_buffer_pos,uv).xyz;
}

vec3 getNormal(vec2 uv)
{
return normalize(texture2D(g_buffer_norm, uv).xyz * 2.0f - 1.0f);
}

vec2 getRandom(vec2 uv)
{
return normalize(texture2D(g_random, g_screen_size * uv / random_size).xy * 2.0f - 1.0f);
}

float doAmbientOcclusion(vec2 tcoord,in vec2 uv, in vec3 p, in vec3 cnorm)
{
vec3 diff = getPosition(tcoord + uv) - p;
vec3 v = normalize(diff);
float d = length(diff)*g_scale;
return max(0.0, dot(cnorm,v)-g_bias)*(1.0/(1.0+d))*g_intensity;
}

void main()
{
vec2 vecs[4];
vecs[0]= vec2(1,0);
vecs[1]= vec2(-1,0);
vecs[2]= vec2(0,1);
vecs[3]= vec2(0,-1);

vec3 p = getPosition(_uv);
vec3 n = getNormal(_uv);
vec2 rand = getRandom(_uv);

float ao = 0.0f;
float rad = g_sample_rad/p.z;

//**SSAO Calculation**//
int iterations = 4;
for (int j = 0; j < iterations; ++j)
{
  vec2 coord1 = reflect(vecs[j],rand)*rad;
  vec2 coord2 = vec2(coord1.x*0.707 - coord1.y*0.707, coord1.x*0.707 + coord1.y*0.707);
  
  ao += doAmbientOcclusion(_uv,coord1*0.25, p, n);
  ao += doAmbientOcclusion(_uv,coord2*0.5, p, n);
  ao += doAmbientOcclusion(_uv,coord1*0.75, p, n);
  ao += doAmbientOcclusion(_uv,coord2, p, n);
}
ao/=iterations*4.0;
//**END**//

//Do stuff here with your occlusion value âaoâ: modulate ambient lighting, write it to a buffer for later //use, etc.
fragColor=vec4(1-ao);
}

I am lost now. sad.png

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Still struggling. Not really sure where I am lost right now. The 4 times split screen looks like it's a position issue, but I am not sure. Maybe my settings are bad or something.. Trying to fix but no avail.

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Was a little bit off from it, but now as I am back, have played a bit with the shader variables, tried multiple things with positions (first thought it was some wrong spaces, apparently not), but I think it's the 4 squares of positions what messes up the look of it. I yet have no idea why final render is split into four parts tho. Could anybody put me on the right track?

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      // [the following code includes all used gl* functions, other parts are due to readability partialy excluded] // glfw: initialize and configure // ------------------------------ glfwInit(); glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 4); glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 4); glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE); // glfw window creation // -------------------- GLFWwindow* window = glfwCreateWindow(SCR_WIDTH, SCR_HEIGHT, "LearnOpenGL", NULL, NULL); if (window == NULL) { cout << "Failed to create GLFW window" << endl; glfwTerminate(); return -1; } glfwMakeContextCurrent(window); glfwSetFramebufferSizeCallback(window, framebuffer_size_callback); glfwSetCursorPosCallback(window, mouse_callback); glfwSetScrollCallback(window, scroll_callback); // tell GLFW to capture our mouse glfwSetInputMode(window, GLFW_CURSOR, GLFW_CURSOR_DISABLED); // glad: load all OpenGL function pointers // --------------------------------------- if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress)) { cout << "Failed to initialize GLAD" << endl; return -1; } // ==================================================================================================== // window and functions are set up // ==================================================================================================== // configure global opengl state // ----------------------------- glEnable(GL_DEPTH_TEST); glEnable(GL_CULL_FACE); // build and compile our shader program [...] // set up vertex data (and buffer(s)) and configure vertex attributes [...] // shader configuration [...] // render loop // =========== while (!glfwWindowShouldClose(window)) { // input processing and fps calculation[...] // render // ------ glClearColor(0.1f, 0.1f, 0.1f, 1.0f); glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glDepthMask(GL_TRUE); //enable depth writing glDepthFunc(GL_LEQUAL); //avoid z-fighting //draw ambient component into color and depth buffer view = camera.GetViewMatrix(); projection = glm::perspective(glm::radians(camera.Zoom), (float)SCR_WIDTH / (float)SCR_HEIGHT, 0.1f, 100.0f); // setting up lighting shader for ambient pass [...] // render the cubes glBindVertexArray(cubeVAO); for (unsigned int i = 0; i < 10; i++) { //position cube [...] glDrawArrays(GL_TRIANGLES, 0, 36); } //------------------------------------------------------------------------------------------------------------------------ glDepthMask(GL_FALSE); //disable depth writing glEnable(GL_BLEND); glBlendFunc(GL_ONE, GL_ONE); //additive blending glEnable(GL_STENCIL_TEST); //setting up shadowShader and lightingShader [...] for (int light = 0; light < lightsused; light++) { glDepthFunc(GL_LESS); glClear(GL_STENCIL_BUFFER_BIT); //configure stencil ops for front- and backface to write according to z-fail glStencilOpSeparate(GL_FRONT, GL_KEEP, GL_DECR_WRAP, GL_KEEP); //-1 for front-facing glStencilOpSeparate(GL_BACK, GL_KEEP, GL_INCR_WRAP, GL_KEEP); //+1 for back-facing glStencilFunc(GL_ALWAYS, 0, GL_TRUE); //stencil test always passes if(hidevolumes) glColorMask(GL_FALSE, GL_FALSE, GL_FALSE, GL_FALSE); //disable writing to the color buffer glDisable(GL_CULL_FACE); glEnable(GL_DEPTH_CLAMP); //necessary to render SVs into infinity //draw SV------------------- shadowShader.use(); shadowShader.setInt("lightnr", light); int nr; if (onecaster) nr = 1; else nr = 10; for (int i = 0; i < nr; i++) { //position cube[...] glDrawArrays(GL_TRIANGLES, 0, 36); } //-------------------------- glDisable(GL_DEPTH_CLAMP); glEnable(GL_CULL_FACE); glStencilFunc(GL_EQUAL, 0, GL_TRUE); //stencil test passes for ==0 so only for non shadowed areas glStencilOp(GL_KEEP, GL_KEEP, GL_KEEP); //keep stencil values for illumination glColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE); //enable writing to the color buffer glDepthFunc(GL_LEQUAL); //avoid z-fighting //draw diffuse and specular pass lightingShader.use(); lightingShader.setInt("lightnr", light); // render the cubes for (unsigned int i = 0; i < 10; i++) { //position cube[...] glDrawArrays(GL_TRIANGLES, 0, 36); } } glDisable(GL_BLEND); glDepthMask(GL_TRUE); //enable depth writing glDisable(GL_STENCIL_TEST); //------------------------------------------------------------------------------------------------------------------------ // also draw the lamp object(s) [...] // glfw: swap buffers and poll IO events (keys pressed/released, mouse moved etc.) // ------------------------------------------------------------------------------- glfwSwapBuffers(window); glfwP } // optional: de-allocate all resources once they've outlived their purpose: // ------------------------------------------------------------------------ glDeleteVertexArrays(1, &cubeVAO); glDeleteVertexArrays(1, &lightVAO); glDeleteBuffers(1, &VBO); // glfw: terminate, clearing all previously allocated GLFW resources. // ------------------------------------------------------------------ glfwTerminate(); return 0;  
    • By Green_Baron
      Hi,
      i am self teaching me graphics and oo programming and came upon this:
      My Window class creates an input handler instance, the glfw user pointer is redirected to that object and methods there do the input handling for keyboard and mouse. That works. Now as part of the input handling i have an orbiting camera that is controlled by mouse movement. GLFW_CURSOR_DISABLED is set as proposed in the glfw manual. The manual says that in this case the cursor is automagically reset to the window's center. But if i don't reset it manually with glfwSetCursorPos( center ) mouse values seem to add up until the scene is locked up.
      Here are some code snippets, mostly standard from tutorials:
      // EventHandler m_eventHandler = new EventHandler( this, glm::vec3( 0.0f, 5.0f, 0.0f ), glm::vec3( 0.0f, 1.0f, 0.0f ) ); glfwSetWindowUserPointer( m_window, m_eventHandler ); m_eventHandler->setCallbacks(); Creation of the input handler during window creation. For now, the camera is part of the input handler, hence the two vectors (position, up-vector).  In future i'll take that functionally out into an own class that inherits from the event handler.
      void EventHandler::setCallbacks() { glfwSetCursorPosCallback( m_window->getWindow(), cursorPosCallback ); glfwSetKeyCallback( m_window->getWindow(), keyCallback ); glfwSetScrollCallback( m_window->getWindow(), scrollCallback ); glfwSetMouseButtonCallback( m_window->getWindow(), mouseButtonCallback ); } Set callbacks in the input handler.
      // static void EventHandler::cursorPosCallback( GLFWwindow *w, double x, double y ) { EventHandler *c = reinterpret_cast<EventHandler *>( glfwGetWindowUserPointer( w ) ); c->onMouseMove( (float)x, (float)y ); } Example for the cursor pos callback redirection to a class method.
      // virtual void EventHandler::onMouseMove( float x, float y ) { if( x != 0 || y != 0 ) { // @todo cursor should be set automatically, according to doc if( m_window->isCursorDisabled() ) glfwSetCursorPos( m_window->getWindow(), m_center.x, m_center.y ); // switch up/down because its more intuitive m_yaw += m_mouseSensitivity * ( m_center.x - x ); m_pitch += m_mouseSensitivity * ( m_center.y - y ); // to avoid locking if( m_pitch > 89.0f ) m_pitch = 89.0f; if( m_pitch < -89.0f ) m_pitch = -89.0f; // Update Front, Right and Up Vectors updateCameraVectors(); } } // onMouseMove() Mouse movement processor method. The interesting part is the manual reset of the mouse position that made the thing work ...
      // straight line distance between the camera and look at point, here (0,0,0) float distance = glm::length( m_target - m_position ); // Calculate the camera position using the distance and angles float camX = distance * -std::sin( glm::radians( m_yaw ) ) * std::cos( glm::radians( m_pitch) ); float camY = distance * -std::sin( glm::radians( m_pitch) ); float camZ = -distance * std::cos( glm::radians( m_yaw ) ) * std::cos( glm::radians( m_pitch) ); // Set the camera position and perspective vectors m_position = glm::vec3( camX, camY, camZ ); m_front = glm::vec3( 0.0, 0.0, 0.0 ) - m_position; m_up = m_worldUp; m_right = glm::normalize( glm::cross( m_front, m_worldUp ) ); glm::lookAt( m_position, m_front, m_up ); Orbiting camera vectors calculation in updateCameraVectors().
      Now, for my understanding, as the glfw manual explicitly states that if cursor is disabled then it is reset to the center, but my code only works if it is reset manually, i fear i am doing something wrong. It is not world moving (only if there is a world to render :-)), but somehow i am curious what i am missing.
       
      I am not a professional programmer, just a hobbyist, so it may well be that i got something principally wrong :-)
      And thanks for any hints and so ...
       
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