GLSL 纹理映射不起作用

Question

我正在尝试使用 GLSL 版本 330 将纹理映射到对象

这里有一些代码可以帮助你理解我的问题

片段着色器：

#version 330
layout(location = 0) in vec3 vertex;
layout(location = 1) in vec3 vertex_normal;
layout(location = 2) in vec2 texCoord;

out vec2 tCoord;

uniform mat4 modelview;
uniform mat4 projection;

void main() {

  gl_Position = projection * modelview * vec4(vertex, 1.0);
  tCoord = texCoord;

}

顶点着色器

#version 330

in vec2 tCoord;

uniform sampler2D texture;

out vec4 color;

void main() {
  if(tCoord == vec2(0,0))
    color = vec4(1.0,0.0,0.0,1.0);
  else
    color = vec4(0.0,1.0,0.0,1.0);
}

将网格和纹理加载到 OpenGL
纹理坐标将使用 vertexAttribPointer 绑定到位置 2（0 是位置，1 是正常）

创建 MeshObj

void MeshObj::setData(const MeshData &meshData) {
  mIndexCount = meshData.indices.size();

  // TODO: extend this method to upload texture coordinates as another VBO //
  // - texture coordinates are at location 2 within the shader code


  // create local storage arrays for vertices, normals and indices //
  unsigned int vertexDataSize = meshData.vertex_position.size();
  unsigned int vertexNormalSize = meshData.vertex_normal.size();
  unsigned int vertexTexcoordSize = meshData.vertex_texcoord.size();

  GLfloat *vertex_position = new GLfloat[vertexDataSize]();
  std::copy(meshData.vertex_position.begin(), meshData.vertex_position.end(), vertex_position);
  GLfloat *vertex_normal = NULL;
  if (vertexNormalSize > 0) {
    vertex_normal = new GLfloat[vertexNormalSize]();
    std::copy(meshData.vertex_normal.begin(), meshData.vertex_normal.end(), vertex_normal);
  }
  GLfloat *vertex_texcoord = NULL;
  if (vertexTexcoordSize > 0) {
    vertex_texcoord = new GLfloat[vertexTexcoordSize]();
    std::copy(meshData.vertex_texcoord.begin(), meshData.vertex_texcoord.end(), vertex_texcoord);
  }
  GLuint *indices = new GLuint[mIndexCount]();
  std::copy(meshData.indices.begin(), meshData.indices.end(), indices);

  // create VAO //
  if (mVAO == 0) {
    glGenVertexArrays(1, &mVAO);
  }
  glBindVertexArray(mVAO);

  // create and bind VBOs and upload data (one VBO per available vertex attribute -> position, normal) //
  if (mVBO_position == 0) {
    glGenBuffers(1, &mVBO_position);
  }
  glBindBuffer(GL_ARRAY_BUFFER, mVBO_position);
  glBufferData(GL_ARRAY_BUFFER, vertexDataSize * sizeof(GLfloat), &vertex_position[0], GL_STATIC_DRAW);
  glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, (void*)0);
  glEnableVertexAttribArray(0);

  if (vertexNormalSize > 0) {
    if (mVBO_normal == 0) {
      glGenBuffers(1, &mVBO_normal);
    }
    glBindBuffer(GL_ARRAY_BUFFER, mVBO_normal);
    glBufferData(GL_ARRAY_BUFFER, vertexNormalSize * sizeof(GLfloat), &vertex_normal[0], GL_STATIC_DRAW);
    glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 0, (void*)0);
    glEnableVertexAttribArray(1);
  }

  if (vertexTexcoordSize > 0) {
    if (mVBO_texcoord == 0) {
      glGenBuffers(1, &mVBO_texcoord);
    }
    std::cout << "Texture stuff set" << std::endl;
    glBindBuffer(GL_ARRAY_BUFFER, mVBO_texcoord);
    glBufferData(GL_ARRAY_BUFFER, vertexTexcoordSize * sizeof(GLfloat), &vertex_texcoord[0], GL_STATIC_DRAW);
    glVertexAttribPointer(2, 2, GL_FLOAT, GL_FALSE, 0, (void*)0);
    glEnableVertexAttribArray(2);
  }

  // init and bind a IBO //
  if (mIBO == 0) {
    glGenBuffers(1, &mIBO);
  }
  glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, mIBO);
  glBufferData(GL_ELEMENT_ARRAY_BUFFER, mIndexCount * sizeof(GLuint), &indices[0], GL_STATIC_DRAW);

  // unbind buffers //
  glBindVertexArray(0);

  // make sure to clean up temporarily allocated data, if neccessary //
  delete[] vertex_position;
  if (vertexNormalSize > 0) {
    delete[] vertex_normal;
  }
  if (vertexTexcoordSize > 0) {
    delete[] vertex_texcoord;
  }
  delete[] indices;
}

渲染场景

  glm_ModelViewMatrix.push(glm_ModelViewMatrix.top());
  glActiveTexture(GL_TEXTURE0);

  glm_ModelViewMatrix.top() = glm::translate(glm_ModelViewMatrix.top(),0.0f,-13.0f,-10.0f);
  glUniformMatrix4fv(uniformLocations["modelview"], 1, false, glm::value_ptr(glm_ModelViewMatrix.top()));

  glBindTexture(GL_TEXTURE_2D, objLoader->getMeshObj("trashbin")->getTexttureID());
  glUniform1i(glGetUniformLocation(shaderProgram,"texture"), objLoader->getMeshObj("trashbin")->getTexttureID());
  objLoader->getMeshObj("trashbin")->render();



  glm_ModelViewMatrix.top() = glm::translate(glm_ModelViewMatrix.top(),-9.0f,-13.0f,-10.0f);
  glm_ModelViewMatrix.top() = glm::scale(glm_ModelViewMatrix.top(), 1.5f,1.5f,1.5f);
  glUniformMatrix4fv(uniformLocations["modelview"], 1, false, glm::value_ptr(glm_ModelViewMatrix.top()));

  glBindTexture(GL_TEXTURE_2D, objLoader->getMeshObj("ball")->getTexttureID());
  glUniform1i(glGetUniformLocation(shaderProgram,"texture"), objLoader->getMeshObj("ball")->getTexttureID());
  objLoader->getMeshObj("ball")->render();

  // restore scene graph to previous state //
  glm_ModelViewMatrix.pop();

渲染网格

void MeshObj::render(void) {
  // render your VAO //
  if (mVAO != 0) {
    glBindVertexArray(mVAO);
    glDrawElements(GL_TRIANGLES, mIndexCount, GL_UNSIGNED_INT, (void*)0);
    glBindVertexArray(0);
  }
}

在所有这些代码之后，现在简要描述一下我的问题： 在我的着色器中，我目前正在检查 texCoord 是否正确传递给着色器，但它始终保持 (0,0)。 上传纹理坐标时问题在哪里？同样的技术适用于 vertexPosition 和 vertex normal...

Answer 1

glUniform1i(glGetUniformLocation(shaderProgram,"texture"), objLoader->getMeshObj("trashbin")->getTexttureID());

尝试传入纹理单元索引 (texUnit) 而不是纹理对象 ID（texObj，来自 glGenTextures() 调用）。

一般：

unsigned int texUnit = 0;
glActiveTexture​( GL_TEXTURE0​ + texUnit );
glBindTexture​( GL_TEXTURE_2D, texObj );
glUniform1i( ..., texUnit );

在你的情况下：

glActiveTexture( GL_TEXTURE0 );
...
glBindTexture( GL_TEXTURE_2D, objLoader->getMeshObj("trashbin")->getTexttureID() );
glUniform1i( glGetUniformLocation( shaderProgram, "texture" ), 0 );

Answer 2

您在任何时候都不会使用 glTexImage2D 将图像提供给 OpenGL

在您的绑定纹理下方添加它，以便为 OpenGL 提供您的纹理

//example parameters, substitute with your own.    
glTexImage2D(GL_TEXTURE_2D, 0,GL_RGB, width, height, 0, GL_BGR, GL_UNSIGNED_BYTE, data);
//just parameters for texture(optional)
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);

参考 glTexImage2D:

http://www.opengl.org/sdk/docs/man/xhtml/glTexImage2D.xml