OpenGL Shadow Mapping Using GLSL

Question

I am trying to get a shadow mapping using GLSL. Unfortunately, the results of my depth processing are unsuitable, even I have pretty decent depth buffer precision. This rendering is like a wireframe, the following image might be a better description.

I also include a test case (one file, including a shader), only the dependency is pyopengl.

# shadow mapping test # utkualtinkaya at gmail # shader is from http://www.fabiensanglard.net/shadowmapping/index.php from OpenGL.GL import * from OpenGL.GLU import * from OpenGL.GLUT import * from OpenGL.GL.shaders import * from OpenGL.GL.framebufferobjects import * import math class Camera: def __init__(self): self.rotx, self.roty = math.pi/4, math.pi/4 self.distance = 100 self.moving = False self.ex, self.ey = 0, 0 self.size = (800, 600) def load_matrices(self): glViewport(0, 0, *self.size) y = math.cos(self.roty) * self.distance x = math.sin(self.roty) * math.cos(self.rotx) * self.distance z = math.sin(self.roty) * math.sin(self.rotx) * self.distance glMatrixMode(GL_PROJECTION) glLoadIdentity() gluPerspective(45.0, self.size[0]/float(self.size[1]), 1, 1000) glMatrixMode(GL_MODELVIEW) glLoadIdentity() gluLookAt(x,y,z, 0,0,0, 0,1,0) def on_mouse_button (self, b, s, x, y): self.moving = not s self.ex, self.ey = x, y if b in [3, 4]: dz = (1 if b == 3 else -1) self.distance += self.distance/15.0 * dz; def on_mouse_move(self, x, y, z = 0): if self.moving: self.rotx += (x-self.ex) / 300.0 self.roty += -(y-self.ey) / 300.0 self.ex, self.ey = x, y def set_size(self, w, h): self.size = w, h class Shader(): def __init__(self): self.is_built = False self.uniforms = {} def build(self): self.program = compileProgram( compileShader(''' uniform mat4 camMatrix; uniform mat4 shadowMatrix; varying vec4 depthProjection; uniform bool useShadow; void main() { gl_Position = camMatrix * gl_ModelViewMatrix * gl_Vertex; depthProjection = shadowMatrix * gl_ModelViewMatrix * gl_Vertex; gl_FrontColor = gl_Color; } ''',GL_VERTEX_SHADER), compileShader(''' varying vec4 depthProjection; uniform sampler2D shadowMap; uniform bool useShadow; void main () { float shadow = 1.0; if (useShadow) { vec4 shadowCoord = depthProjection / depthProjection.w ; // shadowCoord.z -= 0.0003; float distanceFromLight = texture2D(shadowMap, shadowCoord.st).z; if (depthProjection .w > 0.0) shadow = distanceFromLight < shadowCoord.z ? 0.5 : 1.0 ; } gl_FragColor = shadow * gl_Color; } ''',GL_FRAGMENT_SHADER),) self.is_built = True self.uniforms['camMatrix'] = glGetUniformLocation(self.program, 'camMatrix') self.uniforms['shadowMatrix'] = glGetUniformLocation(self.program, 'shadowMatrix') self.uniforms['shadowMap'] = glGetUniformLocation(self.program, 'shadowMap') self.uniforms['useShadow'] = glGetUniformLocation(self.program, 'useShadow') print self.uniforms def use(self): if not self.is_built: self.build() glUseProgram(self.program) class Test: def __init__(self): glutInit(sys.argv) glutInitDisplayMode(GLUT_RGBA | GLUT_DOUBLE | GLUT_ALPHA | GLUT_DEPTH) glutInitWindowSize(800, 600) glutInitWindowPosition(1120/2, 100) self.window = glutCreateWindow("Shadow Test") self.cam = Camera() self.light = Camera() self.cam.set_size(800, 600) self.light.set_size(2048, 2048) self.light.distance = 100 self.shader = Shader() self.initialized = False def setup(self): self.initialized = True glClearColor(0,0,0,1.0); glDepthFunc(GL_LESS) glEnable(GL_DEPTH_TEST) self.fbo = glGenFramebuffers(1); self.shadowTexture = glGenTextures(1) glBindFramebuffer(GL_FRAMEBUFFER, self.fbo) w, h = self.light.size glActiveTexture(GL_TEXTURE5) glBindTexture(GL_TEXTURE_2D, self.shadowTexture) glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST); glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP ); glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP ); glTexImage2D( GL_TEXTURE_2D, 0, GL_DEPTH_COMPONENT, w, h, 0, GL_DEPTH_COMPONENT, GL_UNSIGNED_INT, None) glDrawBuffer(GL_NONE) glReadBuffer(GL_NONE) glFramebufferTexture2D(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_TEXTURE_2D, self.fbo, 0) FBOstatus = glCheckFramebufferStatus(GL_FRAMEBUFFER) if FBOstatus != GL_FRAMEBUFFER_COMPLETE: print ("GL_FRAMEBUFFER_COMPLETE_EXT failed, CANNOT use FBO\n"); glBindFramebuffer(GL_FRAMEBUFFER, 0) #glActiveTexture(GL_TEXTURE0) def draw(self): glPushMatrix() glTranslate(0, 10 ,0) glColor4f(0, 1, 1, 1) glutSolidCube(5) glPopMatrix() glPushMatrix() glColor4f(0.5, 0.5, .5, 1) glScale(100, 1, 100) glutSolidCube(1) glPopMatrix() def apply_camera(self, cam): cam.load_matrices() model_view = glGetDoublev(GL_MODELVIEW_MATRIX); projection = glGetDoublev(GL_PROJECTION_MATRIX); glMatrixMode(GL_MODELVIEW) glLoadIdentity() glMultMatrixd(projection) glMultMatrixd(model_view) glUniformMatrix4fv(self.shader.uniforms['camMatrix'], 1, False, glGetFloatv(GL_MODELVIEW_MATRIX)) glLoadIdentity() def shadow_pass(self): glUniform1i(self.shader.uniforms['useShadow'], 0) glBindFramebuffer(GL_FRAMEBUFFER, self.fbo) glClear(GL_DEPTH_BUFFER_BIT) glCullFace(GL_FRONT) self.apply_camera(self.light) self.draw() glBindFramebuffer(GL_FRAMEBUFFER, 0) def final_pass(self): glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT) self.light.load_matrices() model_view = glGetDoublev(GL_MODELVIEW_MATRIX); projection = glGetDoublev(GL_PROJECTION_MATRIX); glMatrixMode(GL_MODELVIEW) glLoadIdentity() bias = [ 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] glLoadMatrixd(bias) glMultMatrixd(projection) glMultMatrixd(model_view) glUniformMatrix4fv(self.shader.uniforms['shadowMatrix'], 1, False, glGetFloatv(GL_MODELVIEW_MATRIX)) glActiveTexture(GL_TEXTURE5) glBindTexture(GL_TEXTURE_2D, self.shadowTexture) glUniform1i(self.shader.uniforms['shadowMap'], 5) glUniform1i(self.shader.uniforms['useShadow'], 1); self.apply_camera(self.cam) glLoadIdentity() glCullFace(GL_BACK) self.draw() def render(self): if not self.initialized: self.setup() self.shader.use() self.shadow_pass() self.final_pass() glutSwapBuffers() def mouse_move(self, *args): self.cam.on_mouse_move(*args) self.light.on_mouse_move(*args) def mouse_button(self, b, *args): if b==0: self.light.on_mouse_button(b, *args) else: self.cam.on_mouse_button(b, *args) def main(self): glutDisplayFunc(self.render) glutIdleFunc(self.render) glutMouseFunc(self.mouse_button) glutMotionFunc(self.mouse_move) glutReshapeFunc(self.cam.set_size) #self.setup() glutMainLoop() if __name__ == '__main__': test = Test() test.main() 

Answer 1

decided it was a binding problem, in shader shadow pass shader I just checked the boolean value to disable texture reading, but that wasn’t enough. I would have to untie the texture before the shadow passage, which is mentioned in the documentation as:

Quote from OpenGL Refence: Special precautions must be taken to avoid attaching a texture image to the currently connected framebuffer, while the texture object is currently connected and potentially sampled by the current vertex or fragment shader.

NVIDIA ignores this, ATI behaves rather "undefined", as the documentation says.

Answer 2

 // shadowCoord.z -= 0.0003; 

The commented shadow deviation is the solution to your z-fight problem. Change it to some value, for example. + = 0,0005, and you should be good to go.