Question

我需要一个简单的聚光灯着色器的帮助。锥体内的所有顶点应为黄色，锥体外的所有顶点应为黑色。我无法让它发挥作用。我认为这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)   
}

Fragment Shader：

void main(void)
{
   gl_FragColor = gl_Color;
}

修改
蒂姆是对的。此

if(angle > radians(spotCutoff))

应该是：

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，而是当我向前或向后移动时，它似乎相对于我的相机移动，因为锥体变小或变大。

Answer 1

（让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

angle = arccos(dot(A,B))

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

Answer 2

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;

而不是将Angles发送到着色器，最好发送那些Angles的Cos

Answer 3

要回答您的新问题，请点击以下链接：GLSL point light shader moving with camera。解决方案是删除gl_NormalMatrix和gl_ModelViewMatrix。

spotDirection  = normalize(spotDirectionOC * gl_NormalMatrix);

会变成：

spotDirection  = normalize(spotDirectionOC);

Answer 4

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

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

和

//vec3 NSpotDir  = (uViewMatrix * vec4(uLightDirection[index],0)).xyz; //must do outside or become flashlight follow
    vec3 NSpotDir = normalize(uLightDirection[index]);

简单的GLSL Spotlight Shader

4 个答案: