Question

我将一条线传递给几何着色器并输出一个长方体。我在线的每一端创建了4个新点，通过在x或y方向上添加常量“厚度”来传入。如果我在几何着色器中设置厚度，它可以正常工作，但是当我尝试将它作为顶点数据的一部分传递给着色器时，我似乎无法在几何着色器中访问它。当我设置几何着色器中的thickness = vThickness[0]，则不会绘制任何内容。

我可以访问顶点着色器中的厚度数据，它似乎是有效的（我将输出颜色设置为厚度，并且长方体被绘制为白色，这很好，因为它应该是一个整数＆gt; = 1）。问题似乎出现在顶点着色器和几何着色器之间的界面中。

顶点着色器：

#version 150 core

uniform vec3 uColor;

in vec3 position;
in int thickness;

out vec4 vColor;
out int vThickness;

void main() {

    vColor = vec4(uColor, 1.0);
    vThickness = thickness;
    gl_Position = vec4(position, 1.0);
}

几何着色器：

#version 150 core

uniform mat4 uProjection;
uniform mat4 uModel;

in vec4 vColor[];
in int vThickness[];
out vec4 gColor;
out vec3 normalV;
out vec3 points;

layout (lines) in;
layout (triangle_strip, max_vertices = 20) out;

void main() {
    gColor = vColor[0];

    vec3 z = (gl_in[1].gl_Position - gl_in[0].gl_Position).xyz;
    vec3 x = cross(vec3(0.0, 1.0, 0.0), z);

    float thickness = vColor[0];
    // float thickness = 0.5; // This worked 

    x = thickness * normalize(x);
    vec3 y = cross(z, x);
    y = thickness * normalize(y);

    vec4 endTL = uProjection * uModel * (gl_in[1].gl_Position - vec4(x, 0.0) + vec4(y, 0.0));
    vec4 endTR = uProjection * uModel * (gl_in[1].gl_Position + vec4(x, 0.0) + vec4(y, 0.0));
    vec4 endBL = uProjection * uModel * (gl_in[1].gl_Position - vec4(x, 0.0) - vec4(y, 0.0));
    vec4 endBR = uProjection * uModel * (gl_in[1].gl_Position + vec4(x, 0.0) - vec4(y, 0.0));

    vec4 begTL = uProjection * uModel * (gl_in[0].gl_Position - vec4(x, 0.0) + vec4(y, 0.0));
    vec4 begTR = uProjection * uModel * (gl_in[0].gl_Position + vec4(x, 0.0) + vec4(y, 0.0));
    vec4 begBL = uProjection * uModel * (gl_in[0].gl_Position - vec4(x, 0.0) - vec4(y, 0.0));
    vec4 begBR = uProjection * uModel * (gl_in[0].gl_Position + vec4(x, 0.0) - vec4(y, 0.0));

    gl_Position = begTL;    // 0
    points = begTL.xyz;
    normalV = normalize(-x + y);
    EmitVertex();

    gl_Position = endTL;    // 1
    points = endTL.xyz;
    normalV = normalize(-x + y);
    EmitVertex();

    gl_Position = begTR;    // 2
    points = begTR.xyz;
    normalV = normalize(x + y);
    EmitVertex();

    gl_Position = endTR;    // 3
    points = endTR.xyz;
    normalV = normalize(x + y);
    EmitVertex();

    gl_Position = begBR;    // 4
    points = begBR.xyz;
    normalV = normalize(-x + y);
    EmitVertex();

    gl_Position = endBR;    // 5
    points = endBR.xyz;
    normalV = normalize(x - y);
    EmitVertex();

    gl_Position = begBL;    // 6
    points = begBL.xyz;
    normalV = normalize(x - y);
    EmitVertex();       

    gl_Position = endBL;    // 7
    points = endBL.xyz;
    normalV = normalize(-x - y);
    EmitVertex();

    gl_Position = begTL;    // 8
    points = begTL.xyz;
    normalV = normalize(-x + y);
    EmitVertex();

    gl_Position = endTL;    // 9
    points = endTL.xyz;
    normalV = normalize(-x + y);
    EmitVertex();   
}

Fragment Shader：

#version 150 core

vec3 intensities = vec3(0.2f,0.2f,0.2f);
in vec4 gColor;
in vec3 normalV;
in vec3 points;
out vec4 fColor;

void main() {

  vec3 surfaceToLight = normalize(vec3(1,1,0));

  float brightness = dot(normalV, surfaceToLight);
  brightness = clamp(brightness, 0, 1);
  vec4 surfaceColor = gColor;
  fColor = vec4(brightness * intensities + surfaceColor.rgb * 0.5f, surfaceColor.a);

}

我传递的数据：

struct Vertex
{
    Vector3 position;
    uint32 thickness;
};

GLint positionAttribLocation = glGetAttribLocation(renderContext->branchesContext.program, "position");
glEnableVertexAttribArray(positionAttribLocation);
glVertexAttribPointer(positionAttribLocation, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), 0);

GLint thicknessAttribLocation = glGetAttribLocation(renderContext->branchesContext.program, "thickness");
glEnableVertexAttribArray(thicknessAttribLocation);
glVertexAttribPointer(thicknessAttribLocation, 1, GL_UNSIGNED_INT, GL_FALSE, sizeof(Vertex), (void*)(3 * sizeof(float)));

Answer 1

您正在使用不正确的函数为thickness建立顶点属性指针。

glVertexAttribPointer(thicknessAttribLocation, 1, GL_UNSIGNED_INT, GL_FALSE, sizeof(Vertex), (void*)(3 * sizeof(float)));

厚度的类型为int，您使用的是glVertexAttribPointer (...)。该函数旨在将顶点数据转换为浮点数，仅适用于float，vec<N>和矩阵数据类型。

要正确地为您的顶点属性指定数据指针，您需要使用glVertexAttribIPointer (...)。这将仅保留整数数据并将其直接传递给着色器，它适用于{u}int和[i|u]vec<N>属性。

glVertexAttribIPointer(thicknessAttribLocation, 1, GL_UNSIGNED_INT, sizeof(Vertex), (void*)(3 * sizeof(float)));

您会注意到此函数调用中只有一个参数，这是因为浮点归一化不是整数顶点属性的选项。

几何着色器似乎不接受输入属性

1 个答案: