Opengl GLSL细分位移映射

在我最近的项目中，我正在处理硬件端细分。我想要实现的管道应该采用低多边形网格，对其进行细分并应用置换贴图

镶嵌效果很好，就像我期望的那样。但是，当我在细分求值着色器中应用置换贴图时，我会得到一个有点随机的输出

这是没有位移的输出（我使用heightmap作为纹理来验证我的texCoords是否准确）

这是我启用置换时得到的结果（使用相同的纹理进行着色和置换）：

着色器代码如下所示：

//顶点着色器

#version 430

layout(location = 0) in vec4 vertex;
layout(location = 1) in vec4 normal;
layout(location = 2) in vec2 texCoord;

out vec3 vPosition;
out vec3 vNormal;
out vec2 vTexCoord;

void main() {
    vPosition = vertex.xyz;
    vNormal = normal.xyz;
    vTexCoord = texCoord;
}

//苔丝控制

#version 430

layout(vertices = 3) out;

in vec3 vPosition[];
in vec3 vNormal[];
in vec2 vTexCoord[];
out vec3 tcPosition[];
out vec3 tcNormal[];
out vec2 tcTexCoord[];

uniform float innerTessLevel;
uniform float outerTessLevel;

void main(){

    float inTess  = innerTessLevel;
    float outTess = outerTessLevel;

    tcPosition[gl_InvocationID] = vPosition[gl_InvocationID];
    tcNormal[gl_InvocationID]   = vNormal[gl_InvocationID];
    tcTexCoord[gl_InvocationID] = vTexCoord[gl_InvocationID];
    if(gl_InvocationID == 0) {
        gl_TessLevelInner[0] = inTess;
        gl_TessLevelInner[1] = inTess;
        gl_TessLevelOuter[0] = outTess;
        gl_TessLevelOuter[1] = outTess;
        gl_TessLevelOuter[2] = outTess;
        gl_TessLevelOuter[3] = outTess;
    }
}

//苔丝·艾瓦尔

#version 430

layout(triangles, equal_spacing, ccw) in;

in vec3 tcPosition[];
in vec3 tcNormal[];
in vec2 tcTexCoord[];
out vec3 tePosition;
out vec2 teTexCoord;

uniform mat4 ModelViewProjection;
uniform mat4 ModelView;

uniform sampler2D texHeight;

void main(){
    vec3 p0 = gl_TessCoord.x * tcPosition[0];
    vec3 p1 = gl_TessCoord.y * tcPosition[1];
    vec3 p2 = gl_TessCoord.z * tcPosition[2];
    vec3 pos = p0 + p1 + p2;

    vec3 n0 = gl_TessCoord.x * tcNormal[0];
    vec3 n1 = gl_TessCoord.y * tcNormal[1];
    vec3 n2 = gl_TessCoord.z * tcNormal[2];
    vec3 normal = normalize(n0 + n1 + n2);

    vec2 tc0 = gl_TessCoord.x * tcTexCoord[0];
    vec2 tc1 = gl_TessCoord.y * tcTexCoord[1];
    vec2 tc2 = gl_TessCoord.z * tcTexCoord[2];  
    teTexCoord = tc0 + tc1 + tc2;

    float height = texture(texHeight, teTexCoord).x;
    pos += normal * (height * 0.2f);

    gl_Position = ModelViewProjection * vec4(pos, 1);
    tePosition = vec3(ModelView * vec4(pos,1.0)).xyz;
}

//几何学

#version 430

layout(triangles) in;
layout(triangle_strip, max_vertices = 3) out;

uniform mat4 ModelView;

in vec3 tePosition[3];
in vec3 tePatchDistance[3];
in vec2 teTexCoord[3];
out vec3 gFacetNormal;
out vec2 gTexCoord;

void main() {
    vec3 A = tePosition[2] - tePosition[0];
    vec3 B = tePosition[1] - tePosition[0];
    vec4 N = vec4( normalize(cross(A, B)) , 0.0);
    gFacetNormal = N.xyz;

    gTexCoord = teTexCoord[0];
    gl_Position = gl_in[0].gl_Position; EmitVertex();

    gTexCoord = teTexCoord[1];
    gl_Position = gl_in[1].gl_Position; EmitVertex();

    gTexCoord = teTexCoord[2];
    gl_Position = gl_in[2].gl_Position; EmitVertex();

    EndPrimitive();
}

#version 430

layout(triangles) in;
layout(triangle_strip, max_vertices = 3) out;

uniform mat4 ModelView;

in vec3 tePosition[3];
in vec2 teTexCoord[3];
in vec3 teNormal[3];
out vec3 gFacetNormal;
out vec2 gTexCoord;

void main() {

    gFacetNormal = teNormal[0];
    gTexCoord = teTexCoord[0];
    gl_Position = gl_in[0].gl_Position; EmitVertex();

    gFacetNormal = teNormal[1];
    gTexCoord = teTexCoord[1];
    gl_Position = gl_in[1].gl_Position; EmitVertex();

    gFacetNormal = teNormal[2];
    gTexCoord = teTexCoord[2];
    gl_Position = gl_in[2].gl_Position; EmitVertex();

    EndPrimitive();
}

//碎片

#version 430

layout(location = 0) out vec4 fragColor;

in vec3 gFacetNormal;
in vec2 gTexCoord;

uniform float lit;
uniform vec3 light;
uniform sampler2D texHeight;

void main() {
    #ifndef ORANGE_PURPLE
        vec3 color = gl_FrontFacing ? vec3(1.0,0.0,0.0) : vec3(0.0,0.0,1.0);
    #else
        vec3 color = gl_FrontFacing ? vec3(1.0,0.6,0.0) : vec3(0.6,0.0,1.0);
    #endif
    if (lit > 0.5) {
        color = texture(texHeight, gTexCoord).xyz; 
        vec3 N = normalize(gFacetNormal);
        vec3 L = light;
        float df = abs(dot(N,L));
        color = df * color;

        fragColor = vec4(color,1.0);
    }
    else {
        fragColor = vec4(color,1.0);
    }
}

#version 430

layout(location = 0) out vec4 fragColor;

in vec3 gFacetNormal;
in vec2 gTexCoord;

uniform float lit;
uniform vec3 light;
uniform sampler2D texHeight;

void main() {
    #ifndef ORANGE_PURPLE
    vec3 color = gl_FrontFacing ? vec3(1.0,0.0,0.0) : vec3(0.0,0.0,1.0);
    #else
        vec3 color = gl_FrontFacing ? vec3(1.0,0.6,0.0) : vec3(0.6,0.0,1.0);
    #endif
    if (lit > 0.5) {
        color = texture(texHeight, gTexCoord).xyz; 
        vec3 N = normalize(gFacetNormal);
        vec3 L = light;
        float df = abs(dot(N,L));
        color = df * color;
        fragColor = vec4(color,1.0);
    }
    else {
        fragColor = vec4(color,1.0);
    }
}

---

如果有人能在这件事上帮我，那就太好了。

多亏了@AndonM.Coleman，我解决了这个问题

事实上：输出gFacetNormal仅为几何体着色器中的第一个顶点定义。必须按照GLSL规范在每个EmitVertex（…）之后设置输出，否则它们将未定义。许多实现都会重复使用最后一个值集，但如果您希望它能够可移植地工作，则不能依赖于该行为。您需要在每个顶点之前设置一次gFacetNormal。void EmitVertex（）-“将输出变量的当前值发送到当前输出原语。从该调用返回时，输出变量的值未定义。”

我真傻，没注意到这一点，但下面是工作代码：

//顶点

#version 430

layout(location = 0) in vec4 vertex;
layout(location = 1) in vec4 normal;
layout(location = 2) in vec2 texCoord;

out vec3 vPosition;
out vec3 vNormal;
out vec2 vTexCoord;

void main() {
    vPosition = vertex.xyz;
    vNormal = normal.xyz;
    vTexCoord = texCoord;
}

//镶嵌控制

#version 430

layout(vertices = 3) out;

in vec3 vPosition[];
in vec3 vNormal[];
in vec2 vTexCoord[];
out vec3 tcPosition[];
out vec3 tcNormal[];
out vec2 tcTexCoord[];

uniform float innerTessLevel;
uniform float outerTessLevel;

void main(){

    float inTess  = innerTessLevel;
    float outTess = outerTessLevel;

    tcPosition[gl_InvocationID] = vPosition[gl_InvocationID];
    tcNormal[gl_InvocationID]   = vNormal[gl_InvocationID];
    tcTexCoord[gl_InvocationID] = vTexCoord[gl_InvocationID];
    if(gl_InvocationID == 0) {
        gl_TessLevelInner[0] = inTess;
        gl_TessLevelInner[1] = inTess;
        gl_TessLevelOuter[0] = outTess;
        gl_TessLevelOuter[1] = outTess;
        gl_TessLevelOuter[2] = outTess;
        gl_TessLevelOuter[3] = outTess;
    }
}

//镶嵌评估

#version 430

layout(triangles, equal_spacing, ccw) in;

in vec3 tcPosition[];
in vec3 tcNormal[];
in vec2 tcTexCoord[];
out vec3 tePosition;
out vec2 teTexCoord;
out vec3 teNormal;

uniform mat4 ModelViewProjection;
uniform mat4 ModelView;

uniform sampler2D texHeight;

void main(){
    vec3 p0 = gl_TessCoord.x * tcPosition[0];
    vec3 p1 = gl_TessCoord.y * tcPosition[1];
    vec3 p2 = gl_TessCoord.z * tcPosition[2];
    vec3 pos = p0 + p1 + p2;

    vec3 n0 = gl_TessCoord.x * tcNormal[0];
    vec3 n1 = gl_TessCoord.y * tcNormal[1];
    vec3 n2 = gl_TessCoord.z * tcNormal[2];
    vec3 normal = normalize(n0 + n1 + n2);

    vec2 tc0 = gl_TessCoord.x * tcTexCoord[0];
    vec2 tc1 = gl_TessCoord.y * tcTexCoord[1];
    vec2 tc2 = gl_TessCoord.z * tcTexCoord[2];  
    teTexCoord = tc0 + tc1 + tc2;

    float height = texture(texHeight, teTexCoord).x;
    pos += normal * (height * 0.5f);

    gl_Position = ModelViewProjection * vec4(pos, 1);
    teNormal    = vec3(ModelView * vec4(normal,0.0)).xyz;
    tePosition  = vec3(ModelView * vec4(pos,1.0)).xyz;
}

//几何学

#version 430

layout(triangles) in;
layout(triangle_strip, max_vertices = 3) out;

uniform mat4 ModelView;

in vec3 tePosition[3];
in vec3 tePatchDistance[3];
in vec2 teTexCoord[3];
out vec3 gFacetNormal;
out vec2 gTexCoord;

void main() {
    vec3 A = tePosition[2] - tePosition[0];
    vec3 B = tePosition[1] - tePosition[0];
    vec4 N = vec4( normalize(cross(A, B)) , 0.0);
    gFacetNormal = N.xyz;

    gTexCoord = teTexCoord[0];
    gl_Position = gl_in[0].gl_Position; EmitVertex();

    gTexCoord = teTexCoord[1];
    gl_Position = gl_in[1].gl_Position; EmitVertex();

    gTexCoord = teTexCoord[2];
    gl_Position = gl_in[2].gl_Position; EmitVertex();

    EndPrimitive();
}

#version 430

layout(triangles) in;
layout(triangle_strip, max_vertices = 3) out;

uniform mat4 ModelView;

in vec3 tePosition[3];
in vec2 teTexCoord[3];
in vec3 teNormal[3];
out vec3 gFacetNormal;
out vec2 gTexCoord;

void main() {

    gFacetNormal = teNormal[0];
    gTexCoord = teTexCoord[0];
    gl_Position = gl_in[0].gl_Position; EmitVertex();

    gFacetNormal = teNormal[1];
    gTexCoord = teTexCoord[1];
    gl_Position = gl_in[1].gl_Position; EmitVertex();

    gFacetNormal = teNormal[2];
    gTexCoord = teTexCoord[2];
    gl_Position = gl_in[2].gl_Position; EmitVertex();

    EndPrimitive();
}

//碎片

#version 430

layout(location = 0) out vec4 fragColor;

in vec3 gFacetNormal;
in vec2 gTexCoord;

uniform float lit;
uniform vec3 light;
uniform sampler2D texHeight;

void main() {
    #ifndef ORANGE_PURPLE
        vec3 color = gl_FrontFacing ? vec3(1.0,0.0,0.0) : vec3(0.0,0.0,1.0);
    #else
        vec3 color = gl_FrontFacing ? vec3(1.0,0.6,0.0) : vec3(0.6,0.0,1.0);
    #endif
    if (lit > 0.5) {
        color = texture(texHeight, gTexCoord).xyz; 
        vec3 N = normalize(gFacetNormal);
        vec3 L = light;
        float df = abs(dot(N,L));
        color = df * color;

        fragColor = vec4(color,1.0);
    }
    else {
        fragColor = vec4(color,1.0);
    }
}

#version 430

layout(location = 0) out vec4 fragColor;

in vec3 gFacetNormal;
in vec2 gTexCoord;

uniform float lit;
uniform vec3 light;
uniform sampler2D texHeight;

void main() {
    #ifndef ORANGE_PURPLE
    vec3 color = gl_FrontFacing ? vec3(1.0,0.0,0.0) : vec3(0.0,0.0,1.0);
    #else
        vec3 color = gl_FrontFacing ? vec3(1.0,0.6,0.0) : vec3(0.6,0.0,1.0);
    #endif
    if (lit > 0.5) {
        color = texture(texHeight, gTexCoord).xyz; 
        vec3 N = normalize(gFacetNormal);
        vec3 L = light;
        float df = abs(dot(N,L));
        color = df * color;
        fragColor = vec4(color,1.0);
    }
    else {
        fragColor = vec4(color,1.0);
    }
}

---

如果给定一个unorm纹理，置换不应该总是朝向曲面的外侧（现在，在某些区域置换似乎会移动圆柱体内的顶点）？我强烈怀疑你在工商业污水附加费中的正常计算有问题。也许您可以将在TES中计算的法线传递到几何体/片段，并将其可视化，以查看其是否正确？事实上：输出

gFacetNormal

仅为几何体着色器中的第一个顶点定义。必须按照GLSL规范在每个

EmitVertex（…）

之后设置输出，否则它们将未定义。许多实现都会重复使用最后一个值集，但如果您希望它能够可移植地工作，则不能依赖于该行为。您需要在每个

EmitVertex

之前设置

gFacetNormal

一次

void EmitVertex（）

-“将输出变量的当前值发送到当前输出原语。此调用返回时，输出变量的值未定义。”感谢您的建议！！！我本不认为这会起作用，但事实上是“gFacetNormal”破坏了一切。我将为所有对实现例程感兴趣的人编辑代码。老实说，我有点困惑。这是你唯一改变的吗？几何体着色器在细分之后运行，因此不应通过修改GS来解决真正奇怪的置换。但它可能解决的是照明问题。就像我对你的建议发表评论一样，我也很困惑。但是着色器代码是我唯一编辑的东西。关于这些更改，我只修改了逐顶点输出，并且由于我正在通过所有阶段传递法线，因此我删除了几何体着色器中法线的计算。