opengl - 为什么 OpenGL + GLSL 着色器不输出任何内容？

Question

总之，我的全屏着色器没有输出任何东西，

我正在 GLSL 中编写一个延迟着色器，并且我已经到了在屏幕空间中应用灯光的阶段。我有一个环境 channel ，我基本上将漫反射强度从 GBuffer 写入默认 FBO，这很好用。然后我应用另一个全屏四边形来计算场景中的定向光，这也是来自 GBUffer 的样本，并且应该与默认的 FBO 混合。

我遇到的问题是定向光着色器不输出任何内容。我使用与环境 channel 相同的矩阵和转换，但没有任何变化。

我尝试了以下方法；

在环境 channel 中的每个片段上输出相同的颜色以确保它完全输出。 (作品)

在定向光 channel 中的每个片段上输出相同的颜色。 (还是一无所获)

对 XY 顶点坐标使用屏幕分辨率而不是标准化坐标；

这适用于环境传递，因为我可以看到结果按预期变化。

它对定向光传递没有任何改变，我得到相同的输出。

将环境着色器更改为从法线或位置缓冲区采样，以确保可以从(工作)

采样纹理

这是应用程序代码；

glBindFramebuffer(GL_READ_FRAMEBUFFER, m_GeometryBuffer->m_Name);
glBindFramebuffer(GL_DRAW_FRAMEBUFFER, 0);
glDrawBuffers(1,draw_buffers);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

m_AmbientShader->Begin();
    m_AmbientShader->SetUniformInt1("Diffuse",m_DiffuseTexture->m_TextureUnit);
    // Draw full screen quad
    glBegin(GL_QUADS);
        glMultiTexCoord2i(GL_TEXTURE0,0,0);
        glVertex2i(-1,-1);
        glMultiTexCoord2i(GL_TEXTURE0,1,0);
        glVertex2i(1,-1);
        glMultiTexCoord2i(GL_TEXTURE0,1,1);
        glVertex2i(1,1);
        glMultiTexCoord2i(GL_TEXTURE0,0,1);
        glVertex2i(-1,1);
    glEnd();
m_AmbientShader->End();

const DirectionalLight& dl = scene.GetDirectionalLight();

glDrawBuffers(1, draw_buffers);
m_DirectionalLightShader->Begin();
m_DirectionalLightShader->SetUniformInt1("Diffuse",m_DiffuseTexture->m_TextureUnit);
m_DirectionalLightShader->SetUniformInt1("Position",m_PositionTexture->m_TextureUnit);
m_DirectionalLightShader->SetUniformInt1("Normal",m_NormalTexture->m_TextureUnit);
m_DirectionalLightShader->SetUniformFloat3("LightDir",dl.GetDirection());
m_DirectionalLightShader->SetUniformFloat3("LightAmb",dl.GetAmb());
m_DirectionalLightShader->SetUniformFloat3("LightDiff",dl.GetDiff());
m_DirectionalLightShader->SetUniformFloat3("LightSpec",dl.GetSpec());
m_DirectionalLightShader->SetUniformFloat3("LightAtt",dl.GetAtt());
m_DirectionalLightShader->SetUniformFloat1("LightIntensity",dl.GetIntensity());
    // Draw full screen quad
    glBegin(GL_QUADS);
        glMultiTexCoord2i(GL_TEXTURE0,0,0);
        glVertex2i(-1,-1);
        glMultiTexCoord2i(GL_TEXTURE0,1,0);
        glVertex2i(1,-1);
        glMultiTexCoord2i(GL_TEXTURE0,1,1);
        glVertex2i(1,1);
        glMultiTexCoord2i(GL_TEXTURE0,0,1);
        glVertex2i(-1,1);
    glEnd();
m_DirectionalLightShader->End();

如果我的数学错了，请原谅我，我一直在使用着色器来尝试获得任何类型的输出，但这里是着色器源文件；

<-- 方向光.vert -->

varying out vec2 ScreenPos;

varying out vec3 VSLightDir;

uniform vec3 LightDir;
uniform vec3 LightAmb;
uniform vec3 LightDiff;
uniform vec3 LightSpec;
uniform float LightIntensity;

void main()
{
    gl_Position = gl_Vertex;
    ScreenPos = gl_MultiTexCoord0.st;
    VSLightDir = normalize((gl_ModelViewMatrix * vec4(LightDir,0.0)).xyz);
}

<-- 方向光.frag -->

// Gbuffer textures
uniform sampler2D Diffuse;
uniform sampler2D Position;
uniform sampler2D Normal;

in vec2 ScreenPos;
uniform vec3 LightDir;
uniform vec3 LightAmb;
uniform vec3 LightDiff;
uniform vec3 LightSpec;
uniform float LightIntensity;

in vec3 VSLightDir;
out vec4 OutColour;

void main()
{
    // Sample from the GBuffer
    vec4 Diffuse = texture2D(Diffuse, ScreenPos);
    vec4 VSPos = texture2D(Position, ScreenPos);
    vec4 MRT2 = texture2D(Normal, ScreenPos);
    vec3 VSNormal = normalize(MRT2.xyz);
    float Shininess = MRT2.w;

    float LDotN = dot(VSNormal, VSLightDir);

    vec3 View = -normalize(VSPos.xyz);

    // Compute ambient contribution
    vec3 ambient = LightIntensity * LightAmb * Diffuse.xyz;

    // Compute diffuse contribution
    vec3 diffuse = LightIntensity * LightDiff * Diffuse.xyz * max(0.0, LDotN);

    // Compute specular contribution
    vec3 HalfWay = normalize(LightDir + View);
    vec3 specular = (LDotN <= 0.0)
                ? vec3(0.0)
                : LightIntensity * LightSpec * Diffuse.xyz * pow(max(0.0, dot(VSNormal,HalfWay)), Shininess);

    OutColour = vec4(ambient + diffuse + specular, Diffuse.a);
    //OutColour = vec4(0.0,0.0,1.0,1.0); //Debug line
}

<-- 环境.vert -->

varying out vec2 ScreenPos;

void main()
{
    gl_Position = gl_Vertex;

    // Used for the position to sample from GBuffer
    ScreenPos = gl_MultiTexCoord0.st;
}

<-- 环境.frag -->

// Gbuffer textures
uniform sampler2D Diffuse;

in vec2 ScreenPos;

out vec4 OutColour;

void main()
{
    OutColour = texture2D(Diffuse, ScreenPos);
    //OutColour = vec4(0.0,0.0,1.0,1.0);
}

Answer 1

您是否启用了深度测试？我看到您正在清除深度缓冲区，所以我怀疑可能，但是您正在绘制与第一个纹理完全相同的深度的第二个纹理。与 glDepthFunc默认为 GL_LESS这将导致第二次抽签被完全拒绝。

否则，您希望如何将两次抽奖结合起来？是否应该涉及一些混合？