Question

我必须使用OpenGL API和着色器对网格进行纹理化。

为实现这一目标，我做了以下步骤：

加载图片并创建纹理

img::ImageLoader imgLoader;
unsigned char* data = imgLoader.LoadTextureFromFile("../Texturen/brickwork.jpg", &width, &height, true);

glGenTextures(1, &texId);
glBindTexture(GL_TEXTURE_2D, texId);{
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_BGR, GL_UNSIGNED_BYTE, data);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
}

创建顶点，法线和纹理坐标

std::vector<float> v, n, t;

// actual calculation is left out to make it more readable

obj = new GLBatch;
    obj->Begin(GL_TRIANGLES, v.size()/3, t.size()/2);{
    obj->CopyVertexData3f(v.data());
    obj->CopyNormalDataf(n.data());
    obj->CopyTexCoordData2f(t.data(), 0);
}obj->End();

加载着色器

shaders =  gltLoadShaderPairWithAttributes("VertexShader.glsl", "FragmentShader.glsl", 2, 
    GLT_ATTRIBUTE_VERTEX, "vVertex", 
    GLT_ATTRIBUTE_NORMAL, "vNormal",
    GLT_ATTRIBUTE_TEXTURE0, "vTexCoord");

gltCheckErrors(shaders);

（VertexShader.glsl）

#version 130
in vec4 vVertex;
in vec4 vNormal;
in vec2 vTexCoord;

uniform mat4 mvpMatrix;
uniform mat4 mvMatrix;
uniform mat3 normalMatrix;
/// Light position in Eye-Space
uniform vec4 light_pos_vs ;
/// Light diffuse color
uniform vec4 light_diffuse ;
uniform vec4 light_ambient ;
/// Light specular color
uniform vec4 light_specular ;
/// Specular power (shininess)
uniform float spec_power;

/// Material parameters
uniform vec4 mat_emissive;
uniform vec4 mat_ambient; 
uniform vec4 mat_diffuse;   
uniform vec4 mat_specular;  

/// output
out vec4 color;
out vec2 texCoords;

void main()
{   
    texCoords = vTexCoord;
    // Transform vertex from objekt to clip-space
    gl_Position = mvpMatrix * vVertex ;

    // Transform vertex from object to eye-space
    vec4 vertex_vs = mvMatrix * vVertex;
    vec3 ecPos = vertex_vs.xyz / vertex_vs.w;

    // Calculate light direction
    vec3 light_dir_vs = normalize(vec3(light_pos_vs.xyz));

    // Transform normals from object into eye-space
    vec3 normal_vs = normalize(normalMatrix * (vNormal).xyz) ;

    // Viewing vector in eye-space
    vec3 view_dir_vs = normalize(-ecPos );

    // Halfway vektor for Phong-Blinn light modell
    vec3 halfway_vs = normalize(view_dir_vs + light_dir_vs ) ;

    // Diffuse
    float NdotL = max(dot(normal_vs, light_dir_vs),0.0) ;
    vec4 diffuse_color = NdotL * mat_diffuse * light_diffuse ;

    // Specular
    float NdotH = max(dot(normal_vs, halfway_vs),0.0) ;
    vec4 specular_color = pow(NdotH ,spec_power) * mat_specular * light_specular ;

    // Color output
    color = mat_emissive + light_ambient*mat_ambient + diffuse_color + specular_color;
}

（FragmentShader.glsl）

#version 130

in vec2 texCoords;
in vec4 color;

uniform sampler2D textureMap;

out vec4 fragColor;

void main()
{
    fragColor = texture(textureMap, texCoords);
    fragColor *= color;
}

在显示功能中绘制所有内容

glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glEnable(GL_DEPTH_TEST);
glLineWidth(INDICATOR_WIDTH);
glBindTexture(GL_TEXTURE_2D, texId);

modelViewMatrix.LoadIdentity();
modelViewMatrix.Translate(0,0,-5);
modelViewMatrix.PushMatrix();{

    M3DMatrix44f rot;
    m3dQuatToRotationMatrix(rot,rotation);
    modelViewMatrix.MultMatrix(rot);

    // set shader
    glUseProgram(shaders);
    // pass matrices
    glUniformMatrix4fv(glGetUniformLocation(shaders, "mvpMatrix"), 1, GL_FALSE, transformPipeline.GetModelViewProjectionMatrix());
    glUniformMatrix4fv(glGetUniformLocation(shaders, "mvMatrix"),  1, GL_FALSE, transformPipeline.GetModelViewMatrix());
    glUniformMatrix3fv(glGetUniformLocation(shaders, "normalMatrix"),  1, GL_FALSE, transformPipeline.GetNormalMatrix(true));
    // pass light properties
    glUniform4fv(glGetUniformLocation(shaders, "light_pos_vs"),1,light_pos);
    glUniform4fv(glGetUniformLocation(shaders, "light_ambient"),1,light_ambient);
    glUniform4fv(glGetUniformLocation(shaders, "light_diffuse"),1,light_diffuse);
    glUniform4fv(glGetUniformLocation(shaders, "light_specular"),1,light_specular);
    glUniform1f(glGetUniformLocation(shaders, "spec_power"),specular_power);
    // pass material properties
    glUniform4fv(glGetUniformLocation(shaders, "mat_emissive"),1,mat_emissive);
    glUniform4fv(glGetUniformLocation(shaders, "mat_ambient"),1,mat_ambient);
    glUniform4fv(glGetUniformLocation(shaders, "mat_diffuse"),1,mat_diffuse);
    glUniform4fv(glGetUniformLocation(shaders, "mat_specular"),1,mat_specular);

    drawObject();

}modelViewMatrix.PopMatrix();

gltCheckErrors(shaders);
glutSwapBuffers();
glutPostRedisplay();

完成所有这些步骤后，结果看起来很好但没有纹理:(

Screenshot

这里实际发生的是，每个顶点都映射到我的纹理的同一像素，显然是灰色的。

我尝试了从（0,0）到（1,1）和（0,0）到（宽度，高度）的纹理坐标但没有改变。

Answer 1

更改

shaders =  gltLoadShaderPairWithAttributes(
    "VertexShader.glsl", 
    "FragmentShader.glsl",
    2, 
    GLT_ATTRIBUTE_VERTEX, "vVertex", 
    GLT_ATTRIBUTE_NORMAL, "vNormal",
    GLT_ATTRIBUTE_TEXTURE0, "vTexCoord");

到

shaders =  gltLoadShaderPairWithAttributes(
    "VertexShader.glsl", 
    "FragmentShader.glsl",
    3, // < -------------------- 
    GLT_ATTRIBUTE_VERTEX, "vVertex", 
    GLT_ATTRIBUTE_NORMAL, "vNormal",
    GLT_ATTRIBUTE_TEXTURE0, "vTexCoord");

因为函数签名中的第3个参数是紧跟在后面并且应该链接到着色器的属性的数量。在这种情况下，有3个属性：GLT_ATTRIBUTE_VERTEX，GLT_ATTRIBUTE_NORMAL和GLT_ATTRIBUTE_TEXTURE0。仅在原始代码中GLT_ATTRIBUTE_VERTEX，GLT_ATTRIBUTE_NORMAL被链接，因此没有纹理坐标传递给着色器。

Answer 2

首先，绑定纹理时，应指定用于此纹理的纹理单元。这可以通过glActiveTexture

完成

int textureUnit = 0; // <- put the number of the txture unit in here
glActiveTexture( GL_TEXTURE0 + textureUnit );
glGenTextures( 1, &texId );
glBindTexture( GL_TEXTURE_2D, texId );

glGetIntegerv(GL_MAX_COMBINED_TEXTURE_IMAGE_UNITS,...)可以询问纹理单位的最大数量。纹理单元的数量取决于实现，但必须至少为80。因为你只需要一个0就可以了。纹理单元0是默认值，因此如果您从未更改它，则可以跳过此步骤。

接下来请确保您使用了glTexImage2D 以正确的方式，特别是检查格式是否适合您的数据。使用glGetError检查指定目标纹理是否成功。

使用着色器程序时，必须将纹理单元链接到均匀纹理采样器。

int texMapLocation = glGetUniformLocation( shaders, "textureMap" );
...
glUseProgram( shaders );
...
glUniform1i( texMapLocation, textureUnit ); // <- you are missing this

OpenGL纹理映射不起作用

2 个答案: