某些手机​​上的OpenGL ES 2.0灯光非常暗

Question

I write game with android opengl es 2.0 and I have a problem with light brightness on some diffrent devices. I use this formula to calculate light in my fragment shader:

float shineDamper = 0.0;
float reflectivity = 0.001;


float ambient = 0.5;
vec3 unitNormal = normalize(surfaceNormal);
vec3 unitVectorToCamera = normalize(toCameraVector);
vec3 lightColor = vec3(0.5,0.5,0.5);

vec3 unitLightVector = normalize(toLightVector);
float nDot1 = dot(unitNormal,unitLightVector);
float brightness = max(nDot1,0.0);
vec3 lightDirection = -unitLightVector;
vec3 reflectedLightDirection = reflect(lightDirection,unitNormal);
float specularFactor = dot(reflectedLightDirection,unitVectorToCamera);
specularFactor = max(specularFactor,0.0);
float dampedFactor = pow(specularFactor,shineDamper);
vec3 diffuse = brightness * lightColor;
diffuse = max(diffuse,ambient);
vec3 finalSpecular = dampedFactor * reflectivity  * lightColor;
 gl_FragColor =vec4(diffuse,1.0)  * text + vec4(finalSpecular,1.0);

The problem is the light is very dark on some old device but if I change light color to 10 then on old devices is ok but on another phone light is very very bright. Light pos is very far from models because i want get the sun effect.

Solved!!. I just put light calculation to vertex shader.

Answer 1

Most likely it's caused by the fact that some older Android devices only support mediump in the fragment shader which approximates to a half precision float. Probably it was struggling to perform some of the calculations or hold some of the values at that limited precision.

The non-normalized vectors toCameraVector and toLightVector are the most likely culprits.

A decent fix would be to normalize them on the vertex shader (and still normalize in the fragment shader to minimize artifacts from denormalization during interpolation).

If you're getting good visual results by doing the calc in the vertex shader, then that's ideal, because you've probably massively improved performance too.