Opengl - 极端的纹理质量损失

Question

我正在尝试纹理球体。我的顶点着色器：

attribute vec3 a_position;

attribute vec3 a_normal;

attribute vec3 a_texCoord0;

uniform mat4 model;

uniform mat4 view;

uniform mat4 projection;

uniform sampler2D u_texture;

varying vec3 fragPos;

varying vec3 normal;

varying vec3 color;

void main()

{

    gl_Position = projection * view * model * vec4(a_position, 1.0);

    fragPos = vec3(model * vec4(a_position, 1.0));

    normal = a_normal;

    if(a_texCoord0.x > 50){

        color = vec3(1f, 0.0f, 0.0f);

    } else {

        color = texture(u_texture, a_texCoord0);

    }

}

我的片段着色器：

#ifdef GL_ES

    precision mediump float;

#endif

varying vec3 normal;

varying vec3 color;

varying vec3 fragPos;

uniform vec3 lightPos;

uniform vec3 lightColor;

void main()

{

    // Ambient

    float ambientStrength = 0.1;

    vec3 ambient = ambientStrength * lightColor;

    // Diffuse

    vec3 norm = normalize(normal);

    vec3 lightDir = normalize(lightPos - fragPos);

    float diff = max(dot(norm, lightDir), 0.0);

    vec3 diffuse = diff * lightColor;

    //vec3 result = (ambient + diffuse) * color;

    vec3 result = color;

    gl_FragColor = vec4(result, 1.0);

}

结果，我得到了可怕的纹理质量损失。这是原始纹理和我在球体上得到的（这里只是立方体贴图的一部分，其他面是红色的）。我猜想这可能与构建方法（来自二十面体）和纹理（使用立方体贴图）的差异有关。但它可以解释纹理边缘不均匀，但不能解释如此可怕的质量损失。有人可以向我解释这里发生了什么吗？

Answer 1

发生这种情况是因为您在顶点着色器中对纹理进行采样，这意味着您只能在每个三角形的角上获得三种颜色。其他像素被插值。为了获得更好的质量，应该将纹理采样移动到片段着色器，并且应该插值 uv 坐标而不是颜色：顶点着色器：attribute vec3 a_position;attribute vec3 a_normal;attribute vec3 a_texCoord0;uniform mat4 model;uniform mat4 view;uniform mat4 projection;varying vec3 fragPos;varying vec3 normal;varying vec2 texcoord0;void main(){    gl_Position = projection * view * model * vec4(a_position, 1.0);    fragPos = vec3(model * vec4(a_position, 1.0));    normal = a_normal;    texcoord0 = a_texCoord0;}片段着色器：varying vec3 normal;varying vec2 texcoord0;varying vec3 fragPos;uniform sampler2D u_texture;uniform vec3 lightPos;uniform vec3 lightColor;void main(){    vec3 color = texture(u_texture, texcoord0).rgb;    // Ambient    float ambientStrength = 0.1;    vec3 ambient = ambientStrength * lightColor;    // Diffuse    vec3 norm = normalize(normal);    vec3 lightDir = normalize(lightPos - fragPos);    float diff = max(dot(norm, lightDir), 0.0);    vec3 diffuse = diff * lightColor;    //vec3 result = (ambient + diffuse) * color;    vec3 result = color;    gl_FragColor = vec4(result, 1.0);}