OpenGL阴影平移 [英] OpenGL shadow peter-panning

查看：85 发布时间：2020/5/20 23:16:53 c++ opengl glsl shadow

本文介绍了OpenGL阴影平移的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！

问题描述

我通过两次绘制过程将阴影添加到OpenGL中的场景中，一次绘制到深度图，另一次绘制到正常帧缓冲区.

I'm adding shadows to a scene in OpenGL by doing two draw passes, one to a depth map and one to the normal frame buffer.

在使用深度图时不使用任何偏见，会有很多暗疮痤疮.

Without using a bias when using the depth map, there is a lot of shadow acne.

通过在深度图检查中添加偏差来解决此问题.

This is fixed by adding a bias to the depth map check.

但是，当光线移动到另一个角度时，这会导致阴影从对象分离".

However, this causes the shadow to 'detach' from the object when the light is moved to a different angle.

我认为这种效果被称为平移"，是由于在不同角度上使用了较大的偏差所致.

I believe this effect is called peter-panning and is caused by a larger bias being used for different angles.

通常的解决方法似乎是在绘制阴影贴图时剔除朝后的三角形，但是由于地板是2D对象，所以我认为这不能正常工作.

The usual fix for this seems to be to cull back facing triangles when drawing the shadow map, however as the floor plane is a 2D object, I don't believe this would work properly.

我正在使用的实际地形是通过过程生成的，因此创建3D版本并不像在这个简单示例中那样简单.

The actual terrain I am using is procedurally generated and so it is not as simple to create a 3D version of it as in this simple example.

如何将平移固定在这样的2D对象上?

How can the peter-panning be fixed on a 2D object such as this?

顶点着色器

#version 400

layout(location = 0) in vec3 position;
layout(location = 1) in vec3 normal;
layout(location = 2) in vec2 texture_coords;

out VS_OUT {
    vec4 position;
    vec3 normal;
    vec2 texture_coords;
    vec4 shadow_position;
} vs_out;

uniform mat4 model;
uniform mat4 model_view;
uniform mat4 model_view_perspective;
uniform mat3 normal_matrix;
uniform mat4 depth_matrix;

void main() {
    vec4 position_v4 = vec4(position, 1.0);

    vs_out.position = model_view * position_v4;
    vs_out.normal = normal_matrix * normal;
    vs_out.texture_coords = texture_coords;
    vs_out.shadow_position = depth_matrix * model * position_v4;

    gl_Position = model_view_perspective * position_v4;
}

片段着色器

#version 400

in VS_OUT {
    vec4 position;
    vec3 normal;
    vec2 texture_coords;
    vec4 shadow_position;
} fs_in;

out vec4 colour;

uniform mat4 view;
uniform mat4 model_view_perspective;
uniform vec3 light_position;
uniform vec3 emissive_light;
uniform float shininess;
uniform int textured;
uniform sampler2D tex;
uniform sampler2DShadow shadow_texture;

void main() {
    const vec3 specular_albedo = vec3(1.0, 0.8, 0.6);

    colour = vec4(0.8, 0.8, 0.8, 0.8);
    if(textured != 0) {
        colour = texture(tex, fs_in.texture_coords);
    }

    vec3 light_direction = normalize(light_position);
    vec3 normal = normalize(fs_in.normal);

    float visibility = 1.0;
    if(fs_in.shadow_position.z <= 1.0) {
        float bias = max(0.05 * (1.0 - dot(normal, light_direction)), 0.005);
        if(fs_in.shadow_position.z > texture(shadow_texture, fs_in.shadow_position.xyz, 0.0) + bias){
            visibility = 0.0;
        }
    }

    /* Ambient */
    vec3 ambient = colour.xyz * 0.1;

    /* Diffuse */
    vec3 diffuse = visibility * (clamp(dot(normal, light_direction), 0, 1) * colour.xyz);

    /* Specular */
    vec3 specular = vec3(0.0);
    if(dot(normal, light_direction) > 0) {
        vec3 V = normalize(-fs_in.position.xyz);
        vec3 half_dir = normalize(light_direction + V);
        specular = visibility * (pow(max(dot(normal, half_dir), 0.0), shininess) * specular_albedo.xyz);
    }

    colour = vec4(((ambient + diffuse) * colour.xyz) + specular + emissive_light, 1.0);
}

OpenGL阴影平移 [英] OpenGL shadow peter-panning

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OpenGL阴影平移 [英] OpenGL shadow peter-panning

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