METAL - Fragment shader is producing noise

Question

I am trying to use basic lighting techniques described in Metal By Tutorials to produce a diffuse, ambient, and specular light on my models.

I have used this lighting algorithm plenty of times and it works great, but the past 2 times the specular color seems to produce a characteristic green and yellow noise. Even without the specular color, the diffuse and ambient colors seem to produce this awful noise.

Any ideas as to why this would be happening?

I wonder if the fact that I do not use a renderer class is causing this problem.

Here is fragment shader code:

fragment float4 fragmentmain(const VOUT in [[stage_in]],
                             texture2d<float> texture1 [[texture(0)]],
                             constant FRAGMENTUNIFORMS &data [[buffer(2)]],
                             constant LIGHT *lights [[buffer(3)]])
{
     constexpr sampler texturesampler;
     
     float3 basecolor = texture1.sample(texturesampler, in.coords).rgb;
     float3 diffusecolor;
     float3 ambientcolor;
     float3 specularcolor;
     float3 materialspecularcolor = float3(1,1,1);
     float shine = 32;
     float3 normaldirection = normalize(in.normal);
     
     for (uint i = 0 ; i < data.lightcount ; i++) {
          LIGHT light = lights[i];
          if (light.type == sun) {
               float3 lightdirection = normalize(-light.position);
               float diffuseintensity = saturate(-dot(lightdirection, normaldirection));
               diffusecolor = light.color * basecolor * diffuseintensity;
               
               if (diffuseintensity > 0) {
                    float3 reflection = reflect(lightdirection, normaldirection);
                    float3 cameradirection = normalize(in.position.xyz - data.cameraposition);
                    float specularintensity = pow(saturate(-dot(reflection, cameradirection)), shine);
                    specularcolor = light.color * materialspecularcolor * specularintensity;
               }
          } else if (light.type == ambient) {
               ambientcolor = light.color * light.intensity;
          }
     }
     
     float3 color = diffusecolor + ambientcolor + specularcolor;
     return float4(color, 1);
}

Answer 1

Interesting solution to the problem.

I changed:

float3 diffusecolor;
float3 ambientcolor;
float3 specularcolor;

to

float3 diffusecolor = float3(0,0,0);
float3 ambientcolor = float3(0,0,0);
float3 specularcolor = float3(0,0,0);

and the image turned entirely black. No more noise. However, it seemed that my lights were not being iterated through in the for loop.

It turned out that my light.type enum was set to

enum LIGHTTYPE {
     sun = 1, 
     ambient = 2
};

but when I changed it to:

enum LIGHTTYPE {
     sun = 0,
     ambient = 1
};

the issue was totally resolved. Sorry!