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我需要一个简单的聚光灯着色器的帮助。圆锥内的所有顶点都应涂成黄色,圆锥外的所有顶点都应涂成黑色。我只是无法让它工作。我认为它与从世界到眼睛坐标的转换有关。

顶点着色器:

uniform vec4  lightPositionOC;   // in object coordinates
uniform vec3  spotDirectionOC;   // in object coordinates
uniform float spotCutoff;        // in degrees

void main(void)
{
   vec3 lightPosition;
   vec3 spotDirection;
   vec3 lightDirection;
   float angle;

    gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;

    // Transforms light position and direction into eye coordinates
    lightPosition  = (lightPositionOC * gl_ModelViewMatrix).xyz;
    spotDirection  = normalize(spotDirectionOC * gl_NormalMatrix);

    // Calculates the light vector (vector from light position to vertex)
    vec4 vertex = gl_ModelViewMatrix * gl_Vertex;
    lightDirection = normalize(vertex.xyz - lightPosition.xyz);

    // Calculates the angle between the spot light direction vector and the light vector
    angle = dot( normalize(spotDirection),
                -normalize(lightDirection));
    angle = max(angle,0);   

   // Test whether vertex is located in the cone
   if(angle > radians(spotCutoff))
       gl_FrontColor = vec4(1,1,0,1); // lit (yellow)
   else
       gl_FrontColor = vec4(0,0,0,1); // unlit(black)   
}

片段着色器:

void main(void)
{
   gl_FragColor = gl_Color;
}

编辑:
蒂姆是对的。这

if(angle > radians(spotCutoff))

应该:

if(acos(angle) < radians(spotCutoff))

新问题:
灯光似乎没有停留在场景中的固定位置,而是随着我向前或向后移动时锥体变小或变大而相对于我的相机移动。

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4 回答 4

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(设 spotDirection 为向量 A,lightDirection 为向量 B)

您正在分配;

angle = dot(A,B)

公式不应该是:

cos(angle) = dot(A,B)

或者

angle = arccos(dot(A,B))

http://en.wikipedia.org/wiki/Dot_product#Geometric_interpretation

于 2012-05-17T03:24:07.347 回答
1

在我的旧着色器中,我使用了该代码:

float spotEffect = dot(normalize(gl_LightSource[0].spotDirection.xyz), 
                       normalize(-light));
if (spotEffect < gl_LightSource[0].spotCosCutoff) 
{
    spotEffect = smoothstep(gl_LightSource[0].spotCosCutoff-0.002,     
                            gl_LightSource[0].spotCosCutoff, spotEffect);
}
else spotEffect = 1.0;

与其将角度发送到着色器,不如发送这些角度的 Cos

于 2012-05-17T10:38:03.320 回答
1

要回答您的新问题,这里有一个类似问题的链接:GLSL point light shader moving with camera。解决办法是去掉gl_NormalMatrix和gl_ModelViewMatrix。

spotDirection  = normalize(spotDirectionOC * gl_NormalMatrix);

会成为:

spotDirection  = normalize(spotDirectionOC);
于 2015-06-19T06:25:21.523 回答
0

https://code.google.com/p/jpcsp/source/browse/trunk/src/jpcsp/graphics/shader.vert?r=1639

if (spotEffect >= cos(radians(uLightOuterCone[index])))

//vec3 NSpotDir  = (uViewMatrix * vec4(uLightDirection[index],0)).xyz; //must do outside or become flashlight follow
    vec3 NSpotDir = normalize(uLightDirection[index]);
于 2015-02-11T17:53:14.607 回答