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Problem in the shader when rendering?

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gibson

• 9
Problem in the shader when rendering?
« on: April 14, 2018, 17:38:51 »
I moved on. I figured out how to determine if the point is inside the frustum or not. I did it this way: I just calculated the distance to each of the 6 planes, if it turns out to be negative, then the point does not lie inside the frustum. Implemented this all in a fragmented shader.

Below is the implementation of this shader. I transmit 6 square matrices of size 3 A B C D E F - each of them contains 3 vertices of the plane. In the shader, a method was written that finds the distance between the point and the plane of the
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`distancePointPlane`. When the program is started, it independently selects a polygon or does not draw with color. With the transfer of the coordinates of vertices, problems should not exist. The problem at the level of computation in the shader. Help.

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`version 330 corein vec3 normal_modelspace;in vec3 vertex_modelspace;in vec2 TexCoord;in vec4 vertexColor;in vec3 coord;out vec4 color;float distancePointPlane(float pointX, float pointY, float pointZ, float a, float b, float c, float d) {        float denom = sqrt(a * a + b * b + c * c);        return float((a * pointX + b * pointY + c * pointZ + d) / denom);    }float distancePointPlane(vec3 point,mat3 matr) {        float v1Y0Y = matr[1][1] - matr[0][1];        float v2Z0Z = matr[2][2] - matr[0][2];        float v2Y0Y = matr[2][1] - matr[0][1];        float v1Z0Z = matr[1][2] - matr[0][2];        float v2X0X = matr[2][0] - matr[0][0];        float v1X0X = matr[1][0] - matr[0][0];        float a = v1Y0Y * v2Z0Z - v2Y0Y * v1Z0Z;        float b = v1Z0Z * v2X0X - v2Z0Z * v1X0X;        float c = v1X0X * v2Y0Y - v2X0X * v1Y0Y;        float d = -(a * matr[0][0] + b * matr[0][1] + c * matr[0][2]);        float s=0.0;        return distancePointPlane(a, point[1], point[2], a, b, c, d);    }uniform mat3 A;uniform mat3 B;uniform mat3 C;uniform mat3 D;uniform mat3 E;uniform mat3 F;uniform vec3 light_worldspace;uniform sampler2D ourTexture;void main() {  vec3 n = normalize(normal_modelspace);  vec3 l = normalize(light_worldspace - vertex_modelspace);  float cosTheta = clamp( dot( n, l), 0,1 );  float ambient = 0.05;  float aF= distancePointPlane(vertex_modelspace,A);//нахожу расстояние от вершины модели до плоскости а  float bF= distancePointPlane(vertex_modelspace,B);  float cF= distancePointPlane(vertex_modelspace,C);  float dF= distancePointPlane(vertex_modelspace,D);  float eF= distancePointPlane(vertex_modelspace,E);  float fF= distancePointPlane(vertex_modelspace,F);  if(aF>=0.0 && bF>=0.0 && cF>=0.0 && dF>=0.0 && eF>=0.0 && fF>=0.0){   color = vertexColor;  }else{    color = texture(ourTexture, TexCoord)*(cosTheta + ambient);  }}`

KaiHH

• 186
Re: Problem in the shader when rendering?
« Reply #1 on: April 14, 2018, 17:59:19 »
Your solution would become much more elegant, if you did not submit three points on the plane for each of those 6 planes, but instead used 6 vec4's each holding the factors a, b, c and d of the plane equation `a*x + b*y + c*z + d = 0`, making your `distancePointPlane(vec3 point,mat3 matr)` (which computes the plane equation from three points on the plane) completely superfluous.
And as I said in your previous post (which you should just have continued answering to), you can perfectly compute the distances IN THE VERTEX SHADER and only perform the `distance >= 0.0` test ON THE INTERPOLATED VARYING `distance` in the fragment shader. This will be correct, since OpenGL performs perspective-correct interpolation of that varying based on your camera projection. This will save you A LOT of computations in the fragment shader.