我试图实现“单通线框渲染”这个文件,这看起来很简单,但它给了我所期望的厚度,黑暗的值。OpenGL:调试“单通线框渲染”
该文件没有给出确切的代码来找出高度,所以我做了它,因为我认为合适。代码应该将三个顶点投影到视口空间中,获取它们的“高度”并将它们发送给片段着色器。
片段着色器确定最近边缘的距离并生成edgeIntensity。我不确定我应该怎样处理这个值,但是因为它应该在[0,1]之间进行缩放,所以我将反转与我的输出颜色相乘,但它非常弱。
我有几个问题,我不确定在论文中提到。首先,应该用2D而不是3D来计算海拔高度?其次,他们使用DirectX功能,DirectX具有不同的视口空间z范围,是否正确?这很重要吗?我将视出口高度距离乘以视口空间坐标的w值,因为他们建议对透视投影进行校正。
image trying to correct for perspective projection
no correction (not premultiplying by w-value)
非校正的图像好像还没有修正的更远,面对的侧面透视清晰的问题,但角度校正一个具有非常弱的值。
任何人都可以看到我的代码有什么问题,或者如何从这里进行调试?
在GLSL我的顶点代码...
float altitude(in vec3 a, in vec3 b, in vec3 c) { // for an ABC triangle
vec3 ba = a - b;
vec3 bc = c - b;
vec3 ba_onto_bc = dot(ba,bc) * bc;
return(length(ba - ba_onto_bc));
}
in vec3 vertex; // incoming vertex
in vec3 v2; // first neighbor (CCW)
in vec3 v3; // second neighbor (CCW)
in vec4 color;
in vec3 normal;
varying vec3 worldPos;
varying vec3 worldNormal;
varying vec3 altitudes;
uniform mat4 objToWorld;
uniform mat4 cameraPV;
uniform mat4 normalToWorld;
void main() {
worldPos = (objToWorld * vec4(vertex,1.0)).xyz;
worldNormal = (normalToWorld * vec4(normal,1.0)).xyz;
//worldNormal = normal;
gl_Position = cameraPV * objToWorld * vec4(vertex,1.0);
// also put the neighboring polygons in viewport space
vec4 vv1 = gl_Position;
vec4 vv2 = cameraPV * objToWorld * vec4(v2,1.0);
vec4 vv3 = cameraPV * objToWorld * vec4(v3,1.0);
altitudes = vec3(vv1.w * altitude(vv1.xyz,vv2.xyz,vv3.xyz),
vv2.w * altitude(vv2.xyz,vv3.xyz,vv1.xyz),
vv3.w * altitude(vv3.xyz,vv1.xyz,vv2.xyz));
gl_FrontColor = color;
}
和我的片段代码...
varying vec3 worldPos;
varying vec3 worldNormal;
varying vec3 altitudes;
uniform vec3 cameraPos;
uniform vec3 lightDir;
uniform vec4 singleColor;
uniform float isSingleColor;
void main() {
// determine frag distance to closest edge
float d = min(min(altitudes.x, altitudes.y), altitudes.z);
float edgeIntensity = exp2(-2.0*d*d);
vec3 L = lightDir;
vec3 V = normalize(cameraPos - worldPos);
vec3 N = normalize(worldNormal);
vec3 H = normalize(L+V);
//vec4 color = singleColor;
vec4 color = isSingleColor*singleColor + (1.0-isSingleColor)*gl_Color;
//vec4 color = gl_Color;
float amb = 0.6;
vec4 ambient = color * amb;
vec4 diffuse = color * (1.0 - amb) * max(dot(L, N), 0.0);
vec4 specular = vec4(0.0);
gl_FragColor = (edgeIntensity * vec4(0.0)) + ((1.0-edgeIntensity) * vec4(ambient + diffuse + specular));
}
您可以使用'fwidth(min_dist)'作为1像素的厚度,以距离边缘的距离为单位计算,并使用'step(fwidth(min_dist),min_dist)或更好的'smoothstep(fwidth(min_dist), 2 * fwidth(min_dist),min_dist)'。这消除了“魔术数字”'0.005'的需要。 –