Question

我一直在尝试在我的地形LOD程序中实现阴影贴图。我花了很多时间研究不同的技术并玩弄我的代码，但是我找不到我的错误，所以是时候问一下堆栈溢出的opengl大师吧了。）

我使用的是c ++，opengl，GLFW3，GLM，GLEW，GLSL（430）

我用不同的方式搞砸了，但结果总是以下之一：

使用visibility = 0.0;
使用visibility = 1.0;

//////项目摘要

使用跨越＆lt; 0,0,0＆gt;的四边形构建地形。至＆lt; 2048,400,2048＆gt;，然后由tess控制和评估着色器根据charPos进行测试。

我使用不同的* .cpp文件来存储场景不同部分的渲染函数，因此vp_matrix变量在“main.cpp”中计算并传递给每个渲染函数，例如： renderTerrain（vp_matrix）。然后，我根据具体情况使用mvp = vp_matrix * m。对于terrain，我使用m来翻译vp_matrix by＆lt; -charPos.x，0，-charPos.z＆gt;在将地图渲染为颜色之前将地图置于播放器中心。当我渲染到depthBuffer的阴影时，我不使用这个翻译。我使用地图的边界（＆lt; 0,0,0＆gt;到＆lt; 2048,400,2048＆gt;）从太阳的角度渲染整个场景作为正投影。

我使用静态变量，因为我在某些文件中重用某些名称。例如ProgramID，我不希望它们重叠，因此任何未在“简化”代码中定义的变量都是该文件的静态全局。

我应该补充一点，所有着色器都编译没有错误。

//////代码

我尽力将代码缩减为仅影响阴影贴图的部分。相关的2个文件是“main.cpp”和“terrain.cpp”。

“main.cpp”具有FBO初始化和主渲染循环。 “terrain.cpp”包含大部分肉类。

我没有包含样板代码，例如生成VAO。

*********** main.cpp ***********

* init *

ShadowFrameBufferID = 0;
glGenFramebuffers(1, &ShadowFrameBufferID);
glBindFramebuffer(GL_FRAMEBUFFER, ShadowFrameBufferID);

glGenTextures(1, &depthTexture);
glBindTexture(GL_TEXTURE_2D, depthTexture);
glTexImage2D(GL_TEXTURE_2D, 0, GL_DEPTH_COMPONENT32, 1024, 1024, 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_BORDER);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_BORDER);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_COMPARE_FUNC, GL_LEQUAL);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_COMPARE_MODE, GL_COMPARE_REF_TO_TEXTURE);

glFramebufferTexture2D(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_TEXTURE_2D, depthTexture, 0);
glDrawBuffer(GL_NONE);
glReadBuffer(GL_NONE);

if (glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE)
{
    printf("shadow framebuffer error\n");
}

*渲染循环*

glBindFramebuffer(GL_DRAW_FRAMEBUFFER, ShadowFrameBufferID);

glViewport(0, 0, 1024, 1024);
glClear(GL_DEPTH_BUFFER_BIT);

glEnable(GL_DEPTH_TEST);
glDepthFunc(GL_LESS);
glEnable(GL_CULL_FACE);
glCullFace(GL_BACK);

glm::mat4 depthProjectionMatrix = glm::ortho<float>(0.0f, 2048.0f, 0.0f, 400.0f, 0.0f, 2048.0f);
glm::mat4 depthViewMatrix = glm::lookAt(sunPos, glm::vec3(0), glm::vec3(0.0f, 1.0f, 0.0f));
glm::mat4 depth_vp_matrix = depthProjectionMatrix * depthViewMatrix;

renderTerrainShadows(depth_vp_matrix);

glBindFramebuffer(GL_FRAMEBUFFER, 0);

glViewport(0, 0, WINDOW_WIDTH, WINDOW_HEIGHT);

glClearColor(0.478f, 0.702f, 0.816f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

glEnable(GL_DEPTH_TEST);
glDepthFunc(GL_LESS);
glEnable(GL_CULL_FACE);
glCullFace(GL_BACK);

renderTerrain(vp_matrix, depth_vp_matrix, depthTexture);

glfwSwapBuffers(window);
glfwPollEvents();

*********** terrain.cpp ***********

*着色器来源*

// shadow/main vertex shaders (passthrough)
#version 430
layout(location = 0) in vec2 position;
out vec2 vposition;
void main()
{
    vposition = position;\n"
}

// shadow tess evaluation shader
#version 430
uniform mat4 shadowMVP;
void main()
{
    computeXYZ(); // world coordinates

    gl_Position = shadowMVP * vec4(x, y, z, 1.0f);
}

// shadow fragment shader
#version 430
layout(location=0) out float fragmentDepth;
void main()
{
    fragmentDepth = gl_FragCoord.z;
}

// main tess evaluation shader
#version 430
uniform mat4 mvp, shadowBiasMVP;
out vec4 shadowPosition;
void main()
{
    computeXYZ(); // world coordinates

    gl_Position =    mvp * vec4(x, y, z, 1.0f);
    shadowPosition = shadowBiasMVP * vec4(x, y, z, 1.0f);
}

// main fragment shader
#version 430
out vec3 color;
uniform sampler2DShadow shadowMap;
in vec4 shadowPosition;
void main()
{
    color = doStuff(); // compute from diffuse / fog effect / etc

    float visibility = texture(shadowMap, vec3(shadowPosition.xy/shadowPosition.w, shadowPosition.z/shadowPosition.w));
    color = color * visibility;
}

* init *

// shadow program
ShadowProgramID = loadshaders4(shadow_vertex_shader_source, shadow_tessellation_control_shader_source, shadow_tessellation_evaluation_shader_source, shadow_fragment_shader_source);
ShadowMatrixID = glGetUniformLocation(ShadowProgramID, "shadowMVP");

// main program
ProgramID = loadshaders4(vertex_shader_source, tessellation_control_shader_source, tessellation_evaluation_shader_source, fragment_shader_source);
ShadowMapID = glGetUniformLocation(ProgramID, "shadowMap");
MatrixID = glGetUniformLocation(ProgramID, "mvp");
ShadowBiasMatrixID = glGetUniformLocation(ProgramID, "shadowBiasMVP");

* renderTerrainShadows *

void renderTerrainShadows(glm::mat4 depth_vp_matrix)
{
    glUseProgram(ShadowProgramID);

    // uniforms
    glUniformMatrix4fv(ShadowMatrixID, 1, GL_FALSE, &depth_vp_matrix[0][0]);

    // buffers
    glEnableVertexAttribArray(0);
    glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer);
    glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 0, (void*)0);

    glPatchParameteri(GL_PATCH_VERTICES, 4);

    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, elementbuffer);
    glDrawElements(GL_PATCHES, indices.size(), GL_UNSIGNED_INT, (void*)0);

    glDisableVertexAttribArray(0);
}

* renderTerrain *

void renderTerrain(glm::mat4 vp_matrix, glm::mat4 depth_vp_matrix, GLuint depthTexture)
{
    glUseProgram(ProgramID);

    // uniforms
    // mvp matrix for rendering the scene needs to be translated to be centered on player
    glm::mat4 mvp = glm::translate(vp_matrix, glm::vec3(-charPos.x, 0.0f, -charPos.z));
    glUniformMatrix4fv(MatrixID, 1, GL_FALSE, &mvp[0][0]);

    // depth_mvp needs to be biased to change from [-1,1] to [0,1]
    glm::mat4 biasMatrix = glm::mat4(0.5f, 0.0f, 0.0f, 0.0f,
                                     0.0f, 0.5f, 0.0f, 0.0f,
                                     0.0f, 0.0f, 0.5f, 0.0f,
                                     0.5f, 0.5f, 0.5f, 1.0f);
    glm::mat4 depth_mvp = biasMatrix * depth_vp_matrix;
    glUniformMatrix4fv(ShadowBiasMatrixID, 1, GL_FALSE, &depth_mvp[0][0]);

    // shadow texture (0)
    glActiveTexture(GL_TEXTURE0);
    glBindTexture(GL_TEXTURE_2D, depthTexture);
    glUniform1i(ShadowMapID, 0);

    // buffers
    glEnableVertexAttribArray(0);
    glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer);
    glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 0, (void*)0);

    glPatchParameteri(GL_PATCH_VERTICES, 4);

    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, elementbuffer);
    glDrawElements(GL_PATCHES, indices.size(), GL_UNSIGNED_INT, (void*)0);

    glDisableVertexAttribArray(0);
}

Answer 1

太阳位置离glm::ortho

给出的远平面太远了

shadowmapping和sampler2DShadow

1 个答案: