OpenGL中的延迟着色?

我的延迟着色实现遇到了一个奇怪的问题。 我通过MRT将所需的信息渲染到FBO中,当前是世界空间中的漫反射、位置和法线,如下所示:

这是通过对所有树纹理进行以下设置来完成的:

diffuse = std::shared_ptr<bb::Texture>(new bb::Texture(GL_TEXTURE_2D)); // generates texture ID
diffuse->bind();
diffuse->texture2D(0, GL_RGB, width, height, 0, GL_RGB, GL_FLOAT, 0); // glTexture2D
diffuse->parameterf(GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
diffuse->parameterf(GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
diffuse->parameterf(GL_TEXTURE_MIN_FILTER, GL_LINEAR);
diffuse->parameterf(GL_TEXTURE_MAG_FILTER, GL_LINEAR);
diffuse->unbind();
texture2D(GL_COLOR_ATTACHMENT0+1, diffuse->getID(), 0);

然后在我的绘图阶段使用这些:

dsShader->bind();
dsShader->enableVertexAttribArrays();

ds->diffuse->bind(GL_TEXTURE0); // "ds" is an FBO containing the textures
ds->position->bind(GL_TEXTURE0+1);
ds->normal->bind(GL_TEXTURE0+2);

dsShader->sendUniform("diffuse", 0);
dsShader->sendUniform("position", 1);
dsShader->sendUniform("normal", 2);

dsShader->sendUniform("camera", camera3D->position.x, camera3D->position.y, camera3D->position.z);

dsOut->indexBuffer->bind();
dsOut->vertex2Buffer->bind();
dsOut->vertex2Buffer->vertexAttribPointer(dsShader->getAttribLocation("vertex0"), 2, GL_FLOAT, false, 0, 0);

glDrawElements(GL_TRIANGLES, dsOut->indexBuffer->size(), GL_UNSIGNED_INT, 0);

ds->diffuse->unbind();
ds->position->unbind();
ds->normal->unbind();

dsShader->disableVertexAttribArrays();
dsShader->unbind();

使用以下着色器(仅是必要的部分,光源是硬编码的):

struct DirLight{
    vec3 direction;
    vec4 diffuse, specular;
};

uniform sampler2D diffuse;
uniform sampler2D position;
uniform sampler2D normal;

uniform vec3 camera;

DirLight light0 = DirLight(vec3(1, 1, 0), vec4(0.3), vec4(0.1));

in vec2 vertex;

void main(){
    vec4 color = texture(diffuse, vertex)*0.5;
    vec3 p = vec3(texture(position, vertex));
    vec3 n = normalize(vec3(texture(normal, vertex)));

    float ndotl = max(dot(n, normalize(light0.direction)), 0.0); // simple phong

    if(ndotl > 0.0){
        color += ndotl*light0.diffuse;
    }

    gl_FragColor = color;
}

如果我将光源方向设置为负值,那么wierd部分是:

DirLight light0 = DirLight(vec3(-1, 0, 0), vec4(0.3), vec4(0.1));

最终结果不会着色。它看起来适合正值(或多或少)。 以下是输出的图片:

红色区域标记的法线也可能有问题。