QT+OpenGL几何着色器
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几何着色器
- 几何着色器的输入是一个图元（如点或者三角形）的一组顶点
- 几何着色器可以再顶点发送到下一着色器阶段之前对他们随意变换
- 几何着色器最有趣的地方在于，他能够将（这一组）顶点变换为完全不同的图元，并且还能生成比原来更多的顶点
输入布局限定符可以从顶点着色器接收下列任何一个图元值：
● points：绘制GL_POINTS图元时
● lines：绘制GL_LINES或GL_LINE_STRIP时
● lines_adjacency：GL_ADJACENCY或GL_LINESTRIP_ADJACENCY
● triangles：GL_TRIANGLES、GL_TRIANGLE_STRIP或GL_TRIANGLE_FAN
● triangles_adjacency：GL_TRIANGLES_ADJACENCY或GL_TRIANGLE_STRIP_ADJACENCY
#version 330 core layout (points) in; layout (line_strip, max_vertices = 2) out; void main() { gl_Position = gl_in[0].gl_Position + vec4(-0.1, 0.0, 0.0, 0.0); EmitVertex(); gl_Position = gl_in[0].gl_Position + vec4( 0.1, 0.0, 0.0, 0.0); EmitVertex(); EndPrimitive(); }
和输入布局修饰符一样，输出布局修饰符也可以接受几个图元值
- points
- line_strip
- triangle_strip
为了生成更有意义的结果，我们需要某种方式来获取前一着色器阶段的输出。GLSL提供给我们一个内建变量在内部看来可能是这样的：
in gl_Vertex { vec4 gl_Posititon; float gl_PointSize; float gl_ClipDistance[]; }gl_in[];
它被声明成一个数组，因为大多数的渲染图元包含多于一个的顶点，而几何着色器的输入是一个图元的所有顶点。
每次我们调用EmitVertex时候，gl_Position中的向量会被添加到图元中，当EndPrimitive()被调用时候，所有发射出的(Emitted)顶点都会合成指定的输出渲染图元。
#version 330 core layout (points) in; layout (triangle_strip, max_vertices = 5) out; in VS_OUT { vec3 color; } gs_in[]; out vec3 fColor; void build_house(vec4 position) { fColor=gs_in[0].color; gl_Position = position + vec4(-0.2, -0.2, 0.0, 0.0); // 1:bottom-left EmitVertex(); gl_Position = position + vec4( 0.2, -0.2, 0.0, 0.0); // 2:bottom-right EmitVertex(); gl_Position = position + vec4(-0.2, 0.2, 0.0, 0.0); // 3:top-left EmitVertex(); gl_Position = position + vec4( 0.2, 0.2, 0.0, 0.0); // 4:top-right EmitVertex(); gl_Position = position + vec4( 0.0, 0.4, 0.0, 0.0); // 5:top fColor=vec3(1.0, 1.0, 1.0); EmitVertex(); EndPrimitive(); } void main() { build_house(gl_in[0].gl_Position); }
爆破物体效果
几何着色器
#version 330 core layout (triangles) in; layout (triangle_strip, max_vertices = 3) out; in VS_OUT { vec2 texCoords; } gs_in[]; out vec2 TexCoords; uniform float time; vec3 GetNormal() { vec3 a = vec3(gl_in[0].gl_Position) - vec3(gl_in[1].gl_Position); vec3 b = vec3(gl_in[2].gl_Position) - vec3(gl_in[1].gl_Position); return normalize(cross(a, b)); } vec4 explode(vec4 position, vec3 normal) { float magnitude = 4.0; vec3 direction = normal * ((sin(time) + 1.0) / 2.0) * magnitude; return position + vec4(direction, 0.0); } void main() { vec3 normal = GetNormal(); gl_Position = explode(gl_in[0].gl_Position, normal); TexCoords = gs_in[0].texCoords; EmitVertex(); gl_Position = explode(gl_in[1].gl_Position, normal); TexCoords = gs_in[1].texCoords; EmitVertex(); gl_Position = explode(gl_in[2].gl_Position, normal); TexCoords = gs_in[2].texCoords; EmitVertex(); EndPrimitive(); }
片段着色器
#version 330 core struct Material { sampler2D texture_diffuse1; sampler2D texture_specular1; float shininess; }; struct Light { vec3 direction; vec3 ambient; vec3 diffuse; vec3 specular; }; uniform Light light; uniform Material material; out vec4 FragColor; in vec2 TexCoords; in vec3 Normal; in vec3 FragPos; uniform vec3 viewPos; void main() { vec3 diffuseTexColor=vec3(texture(material.texture_diffuse1,TexCoords)); vec3 specularTexColor=vec3(texture(material.texture_specular1,TexCoords)); // ambient vec3 ambient = diffuseTexColor*light.ambient; // diffuse vec3 norm = normalize(Normal); vec3 lightDir = normalize(-light.direction); float diff = max(dot(norm, lightDir), 0.0); vec3 diffuse = diff *diffuseTexColor*light.diffuse; // specular vec3 viewDir = normalize(viewPos - FragPos); vec3 reflectDir = reflect(-lightDir, norm); float spec = pow(max(dot(viewDir, reflectDir), 0.0), material.shininess); vec3 specular = spec*specularTexColor*light.specular; vec3 result = (ambient + diffuse + specular); FragColor = vec4(result, 1.0); }
顶点着色器
#version 330 core layout (location = 0) in vec3 aPos; layout (location = 1) in vec3 aNormal; layout (location = 2) in vec2 aTexCoords; out VS_OUT { vec2 texCoords;} vs_out; out vec3 Normal; out vec3 FragPos; out vec2 TexCoords; uniform mat4 model; uniform mat4 view; uniform mat4 projection; void main() { vs_out.texCoords=aTexCoords; TexCoords=aTexCoords; Normal = mat3(transpose(inverse(model))) * aNormal; FragPos=vec3(model * vec4(aPos,1.0)); gl_Position = projection * view * model * vec4(aPos, 1.0); gl_PointSize=20.0; }
法向量可视化
顶点着色器
#version 330 core layout (location = 0) in vec3 aPos; layout (location = 1) in vec3 aNormal; out VS_OUT { vec3 normal;} vs_out; uniform mat4 model; uniform mat4 view; void main() { vs_out.normal = mat3(transpose(inverse(view*model))) * aNormal; // mat3 normalMatrix = mat3(transpose(inverse(view * model))); // vs_out.normal = normalize(vec3(vec4(normalMatrix * aNormal, 0.0))); gl_Position = view * model * vec4(aPos, 1.0); }
几何着色器
#version 330 core layout (triangles) in; layout (line_strip, max_vertices = 6) out; in VS_OUT { vec3 normal; } gs_in[]; const float MAGNITUDE = 0.4; uniform mat4 projection; void GenerateLine(int index) { gl_Position = projection * gl_in[index].gl_Position; EmitVertex(); gl_Position = projection * (gl_in[index].gl_Position + vec4(gs_in[index].normal, 0.0) * MAGNITUDE); EmitVertex(); EndPrimitive(); } void main() { GenerateLine(0); // first vertex normal GenerateLine(1); // second vertex normal GenerateLine(2); // third vertex normal }
片段着色器
#version 330 core out vec4 FragColor; void main() { FragColor = vec4(1.0,1.0,0.0, 1.0); }
