渲染阴影的 OpenGL 正射投影问题

Question

I've been trying to implement shadow mapping into my OpenGL engine in SFML 2.2 , and they don't seem to be rendering right. I believe I narrowed down the issue to the ortho projection used to calculate the shadows.

/* before the main loop, creating the depth buffer for shadow mapping */
glm::vec3 lightPos(glm::vec3(-45.f, 45.f, -40.f));

const GLuint SHADOW_WIDTH = 1024, SHADOW_HEIGHT = 1024;
GLuint depthMapFBO;
glGenFramebuffers(1, &depthMapFBO);

GLuint depthMap;
glGenTextures(1, &depthMap);
glBindTexture(GL_TEXTURE_2D, depthMap);

glTexImage2D(GL_TEXTURE_2D, 0, GL_DEPTH_COMPONENT, SHADOW_WIDTH, SHADOW_HEIGHT, 0, GL_DEPTH_COMPONENT, GL_FLOAT, NULL);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_BORDER);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_BORDER);
GLfloat borderColor[] = { 1.0, 1.0, 1.0, 1.0 };
glTexParameterfv(GL_TEXTURE_2D, GL_TEXTURE_BORDER_COLOR, borderColor);

glBindFramebuffer(GL_FRAMEBUFFER, depthMapFBO);
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_TEXTURE_2D, depthMap, 0);
glDrawBuffer(GL_NONE);
glReadBuffer(GL_NONE);
glBindFramebuffer(GL_FRAMEBUFFER, 0);

glClearColor(0.1f, 0.1f, 0.1f, 1.0f);

/* in the main loop, sending information to the appropiate shaders and setting viewports */
glm::mat4 lightProjection, lightView;
glm::mat4 lightSpaceMatrix;
GLfloat near_plane = 1.f, far_plane = 300.f;
lightProjection = glm::ortho(-10.f, 10.f, -10.f, 10.f, near_plane, far_plane);
lightView       = glm::lookAt(lightPos, glm::vec3(0.0f), glm::vec3(0.0, 1.0, 0.0));
lightSpaceMatrix = lightProjection * lightView;

glUseProgram(simpleDepthShader);
glUniformMatrix4fv(glGetUniformLocation(simpleDepthShader, "lightSpaceMat"), 1, GL_FALSE, glm::value_ptr(lightSpaceMatrix));
glViewport(0, 0, SHADOW_WIDTH, SHADOW_HEIGHT);
glBindFramebuffer(GL_FRAMEBUFFER, depthMapFBO);
    glClear(GL_DEPTH_BUFFER_BIT);
    RenderScene();
glBindFramebuffer(GL_FRAMEBUFFER, 0);

// reset viewport, and display the scene as normal
glViewport(0, 0, window.getSize().x, window.getSize().y);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

glUniform3fv(glGetUniformLocation(lightingShader, "lightPos_shade"), 1, &lightPos[0]);
glUniform3fv(glGetUniformLocation(lightingShader, "viewPos"), 1, &getPos()[0]);
glUniformMatrix4fv(glGetUniformLocation(lightingShader, "lightSpaceMat"), 1, GL_FALSE, glm::value_ptr(lightSpaceMatrix));
glActiveTexture(GL_TEXTURE1);
glBindTexture(GL_TEXTURE_2D, depthMap);

RenderScene();

I've applied the view and projection matrix to the camera to see what the light sees, and this was the result (along with the view from the depth buffer) .

Here's what the scene looks like with the shadows (which the shadow for the stall doesn't even cast onto itself for some reason).

Answer 1

It seems that your shader doesn't fetch your shadow pixels correctly.

When you transform your vertices with your light matrix they are in the [-1, 1] range, but texture sampling is in the range [0, 1].

http://www.opengl-tutorial.org/intermediate-tutorials/tutorial-16-shadow-mapping/