c++ - 显示 OpenGL 纯色而不是纹理

Question

因此，我查看了本网站和其他网站上的所有类似问题，但我没有找到我的纹理无法加载的原因的答案。我确定纹理被正确读取，但是，它只是没有正确应用。这是我的代码:

获取纹理:

 glGenTextures(NumTextures, textures);

glActiveTexture( GL_TEXTURE0 );

// load and bind tree texture
readPPM6("textures/tree_trunk.pbm", treeTex);

glBindTexture(GL_TEXTURE_2D, textures[0]);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_BASE_LEVEL, 0);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAX_LEVEL, 0);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, 128, 128, 0, GL_RGB,
    GL_UNSIGNED_BYTE, treeTex);

绑定(bind)对象:

// VAO[Tree]
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, vElements[TreeE]);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(GLushort)*treeIndices.size(), treeIndices.data(), GL_STATIC_DRAW);

glBindVertexArray(vArrays[TreeA]);
glBindBuffer(GL_ARRAY_BUFFER, vBuffers[TreeB]);
glBufferData(GL_ARRAY_BUFFER, sizeof(GLfloat)*treeVertices.size() + sizeof(vec2) * 90, NULL, GL_STATIC_DRAW);
glBufferSubData(GL_ARRAY_BUFFER, 0, sizeof(GLfloat)*treeVertices.size(), treeVertices.data());
glBufferSubData(GL_ARRAY_BUFFER, sizeof(GLfloat)*treeVertices.size(), sizeof(vec2)*90,
    treeTexCoords);
glUseProgram( texture );
vPosition = glGetAttribLocation( texture, "vPosition" );
glVertexAttribPointer( vPosition, 4, GL_FLOAT, GL_FALSE, 0, 0);
glEnableVertexAttribArray(vPosition);
vTexCoord = glGetAttribLocation( texture, "vTexCoord" );
glVertexAttribPointer( vTexCoord, 2, GL_FLOAT, GL_FALSE, 0,
    (const void*) ((sizeof(GLfloat) * treeVertices.size())));
glEnableVertexAttribArray( vTexCoord ); 
glUniform1i(glGetUniformLocation(texture, "texture"), 0);
glBindVertexArray(0);

画树:

glUseProgram(texture);

proj_loc = glGetUniformLocation(texture, "projection");
model_view_loc = glGetUniformLocation(texture, "modelview");
glUniformMatrix4fv(proj_loc, 1, GL_TRUE, projmat);
glUniformMatrix4fv(model_view_loc, 1, GL_TRUE, modelmat);

glEnable(GL_PRIMITIVE_RESTART);
glPrimitiveRestartIndex(0xFFFF);

glBindVertexArray(vArrays[TreeA]);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, vElements[TreeE]);

glEnable(GL_TEXTURE_2D);    

glActiveTexture( GL_TEXTURE0 ); 

glBindTexture(GL_TEXTURE_2D, textures[0]);
glDrawElements(GL_TRIANGLE_STRIP, treeIndices.size(), GL_UNSIGNED_SHORT, NULL);

glDisable(GL_PRIMITIVE_RESTART);
glDisable(GL_TEXTURE_2D);

glUseProgram(0);
glBindVertexArray(0);

树的创建方式:

getCylinderVertices(treeVertices, 10.0, 3.0, 10);
getCylinderIndices(treeIndices, 10);

getConeVertices(treeVertices, 10.0, 15.0, 6.0, 10);
for (int i = 0; i < 10; i++)
{
    treeIndices.push_back(60+i*3);
    treeIndices.push_back(60+i*3+1);
    treeIndices.push_back(60+i*3+2);
    treeIndices.push_back(0xFFFF);
}

treeTexCoords = new vec2[90];
for (int i = 0; i < 10; i++)
{
    treeTexCoords[i*6] = vec2(0.0, 0.0);
    treeTexCoords[i*6+1] = vec2(0.0, 0.2);
    treeTexCoords[i*6+2] = vec2(0.0, 0.0);
    treeTexCoords[i*6+3] = vec2(1.0, 0.2);
    treeTexCoords[i*6+4] = vec2(1.0, 0.0);
    treeTexCoords[i*6+5] = vec2(0.0, 0.0);
}

for (int i = 0; i < 30; i++)
{
    treeTexCoords[60+i] = vec2(0.0,0.0);
}

顶点着色器:

    #version 330 core

attribute vec4 vPosition;
uniform mat4 projection;
uniform mat4 modelview;

attribute vec4 vertex;
attribute vec3 normal;
attribute vec2 vTexCoord;

out vec2 texCoord;

void main() 
{ 
    texCoord    = vTexCoord;
    gl_Position = projection*modelview*vPosition;
}

片段着色器:

 #version 330 core

in  vec2 texCoord;

uniform sampler2D texture;

void main() 
{ 
    gl_FragColor = texture2D(texture, texCoord);
}

修复缓冲区子数据分配问题后，树现在是这样的: http://i.imgur.com/dMBq9xN.jpg

作为引用，这是我正在使用的图像: http://i.imgur.com/QuuQQ5i.jpg

我已经解决了最后一个问题，读者正在阅读作为图像一部分的尾行，因此一切都转移到下一个颜色。谢谢大家的帮助。

Answer 1

我很惊讶这段代码没有导致崩溃，sizeof (vec2) * 90是你在第二次调用 glBufferSubData (...) 时应该使用的因为纹理坐标数组中的浮点分量数是顶点位置数组中分量数的一半。当您用数据填充缓冲区时，您正在溢出 VBO 的存储和客户端内存中的纹理坐标数组。

sizeof (treeTexCoords)绝对不是你想要的，因为你已经动态分配了那个数组!虽然您可以使用 sizeof (...)如果您尝试使用指向由 new 分配的内存的指针来获取静态大小数组的大小，您将得到的只是指针本身的大小。因此，sizeof (treeTexCoords)在您的系统上可能是 4 或 8。

glBindVertexArray (vArrays [TreeA]);
glBindBuffer      (GL_ARRAY_BUFFER, vBuffers [TreeB]);

//
// @CORRECTION #1
//
glBufferData      (GL_ARRAY_BUFFER, sizeof (GLfloat) * treeVertices.size () + 
                                    sizeof (vec2)    * 90,
                                        NULL, GL_STATIC_DRAW);
glBufferSubData   (GL_ARRAY_BUFFER, 0,
                                    sizeof (GLfloat) * treeVertices.size (),
                                        treeVertices.data ());
//
// @CORRECTION #2
//
glBufferSubData   (GL_ARRAY_BUFFER, sizeof (GLfloat) * treeVertices.size (), 
                                    sizeof (vec2)    * 90,
                                        treeTexCoords);

修正 #1 分配了适当的存储量(而不是为所有顶点分配足够的存储空间 + 1 个指针)。

更正 #2 只读到 treeTexCoords 的末尾而不是超越它。

根据 treeVertices 的方式，可能会出现其他问题已声明 - 您可以编辑您的问题以显示 treeVertices 的声明吗？ ？我假设它类似于 std::vector <GLfloat> .