I'm quite new to OpenGL ES and I'm trying to add some shadows to my current scene. I decided to do that with the help of a cubemap. I'm using OpenGL es 2.0, so geometry shader or the gl_FragDepth variable is unavailable for me. I've googled some so I got some insight about the topic and reading this (http://www.cg.tuwien.ac.at/courses/Realtime/repetitorium/2010/OmnidirShadows.pdf) proved quite useful. Basically I rely on this linked doc.
But something is wrong with my code, because in the rendered scene every pixel is under shadow. I think the problem can be found in my shaders, but I paste here all my relevant code to see everything clearly.
Setup framebuffer and creating the cubemap:
GLuint FBO;
GLuint cubeTexture;
glGenFramebuffers(1, &FBO);
glBindFramebuffer(GL_FRAMEBUFFER, FBO);
// Depth texture
glGenTextures(1, &cubeTexture);
glBindTexture(GL_TEXTURE_CUBE_MAP, cubeTexture);
glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
//glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_WRAP_R, GL_CLAMP_TO_EDGE); // no GL_TEXTURE_WRAP_R
// right, left, top, bottom, front, back
for (int face = 0; face < 6; ++face) {
// create space for the textures, content need not to be specified (last parameter is 0)
glTexImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_X + face, 0, GL_DEPTH_COMPONENT16, 1024, 768, 0, GL_DEPTH_COMPONENT, GL_FLOAT, 0);
}
glBindTexture(GL_TEXTURE_CUBE_MAP, 0);
glBindFramebuffer(GL_FRAMEBUFFER, 0);
In the Display function I try to achieve 6 render passes to fill the shadow maps (the 6 sides of the cube).
Rendering:
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
glClearDepthf(1.0f);
glm::vec3 camPos = ... // position of the camera, it is in world space
glm::vec4 lightPos = ... // position of the light source, it is in world space
// 1. render into texture
float zNear = 0.1f;
float zFar = 100.0f;
// or should I use ortho instead of perspective?
glm::mat4 projMatrix = glm::perspective(90.0f, (float)esContext->width / esContext->height, zNear, zFar);
// The 6 cameras have to be placed to the light source and they need the proper view matrices
glm::mat4 cubeMapMatrices[6]; // contains six basic and defined rotation matrices for the six directions
cubeMapMatrices[0] = glm::make_mat4(rotPositiveX);
cubeMapMatrices[1] = glm::make_mat4(rotNegativeX);
cubeMapMatrices[2] = glm::make_mat4(rotPositiveY);
cubeMapMatrices[3] = glm::make_mat4(rotNegativeY);
cubeMapMatrices[4] = glm::make_mat4(rotPositiveZ);
cubeMapMatrices[5] = glm::make_mat4(rotNegativeZ);
glm::vec4 translation = lightPos;
glBindTexture(GL_TEXTURE_CUBE_MAP, cubeTexture);
glBindFramebuffer(GL_FRAMEBUFFER, FBO);
for (int face = 0; face < 6; ++face) {
glClear(GL_DEPTH_BUFFER_BIT); // do I need this here?
cubeMapMatrices[face][3] = translation; // the translation part is the same for all
cubeMapMatrices[face] = projMatrix * cubeMapMatrices[face]; // now it's an mvp matrix
glUniformMatrix4fv(cubeProjectionMatrixID, 1, GL_FALSE, glm::value_ptr(cubeMapMatrices[face]));
// Attach depth cubemap texture to FBO's depth attachment point
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_TEXTURE_CUBE_MAP_POSITIVE_X + face, cubeTexture, 0);
int err = glCheckFramebufferStatus(GL_FRAMEBUFFER);
if (err != GL_FRAMEBUFFER_COMPLETE) {
std::cout << "Framebuffer error, status: " << err << std::endl;
}
RenderScene(); // do the drawing
}
glBindFramebuffer(GL_FRAMEBUFFER, 0);
// 2. render into screen
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
RenderScene(); // do the drawing
// swap the buffers
So here come the different shaders. I have one vertex shader and one fragment shader for the depth calculation and one vertex shader and one fragment shader for the screen rendering. My problem is that I'm not sure how to write into the cubemap, if the framebuffer is in use, then will the gl_Position determine the coordinates in the given cube face?
vertex shader for depth calculating:
in vec3 vPosition;
uniform mat4 mModel;
uniform mat4 mCubeProjection;
uniform vec4 vLight;
out vec4 vFrag Position; // world space
out vec4 vLightPosition; // mvp transformed
void main()
{
vec4 position = vec4(vPosition, 1.0);
vFragPosition = mModel* position;
vLightPosition = vLight;
gl_Position = mCubeProjection * vFragPosition;
}
fragment shader for depth calculating:
in vec4 vFragPosition; // world space
in vec4 vLightPosition; // world space
out float depthValue;
void main()
{
depthValue = distance(vFragPosition.xyz, vLightPosition.xyz); // need normalization?
}
vertex shader for rendering to the screen:
uniform mat4 mModel;
uniform mat4 mView;
uniform mat4 mProjection;
uniform vec4 vLight; // it is in world space
out vec3 lw; // light position in world space
out vec3 pw; // pixel position in world space
void main()
{
vec4 position = vec4(vPosition, 1.0);
lw = vLight.xyz;
pw = (mModel* position).xyz;
gl_Position = mProjection* mView * mModel* position;
}
fragment shader for rendering to the screen:
in vec3 lw;
in vec3 pw;
uniform samplerCube cubeMap;
out vec4 outputColor;
void main()
{
vec3 lookup = pw - lw;
float smValue = texture(cubeMap, lookup).r; // retrieves texels from a texture (d, d, d, 1.0)
float distance = length(lookup); // dist from the fragment to the light
float eps = 0.1;
float shadowVal = 1.0;
if (smValue + eps < distance) {
shadowVal = 0.1; // in shadow
}
// here comes the lighting stuff
// ...
outputColor = outputColor * shadowVal;
}
So again, the issue is that every pixel falls under shadow. From the code I excluded some uniform passes to the shader, but they are ok. Can you give me an advice what should I fix in the code? Are my shaders (especially for the first pass) correct, do I set the transformations for the cube mapping properly? Thank you.
P.S: This is my first question here, I hope it is clear enough and fulfils the requirements of a correctly posted question.
