I would like to be able to get this as a function with an objects 3D coordinates and size so I would know if I have to bother rendering it.

This is typically called “frustum culling”, this site has an explanation and I’m sure there are many others.

```
// bsphere position (in view space)
vec3 center = boundingsphere.xyz;
float radius = boundingsphere.w;
vec3 position = (modelview * vec4(center, 1)).xyz;
float A = 1.0f / tan(FieldOfView * AspectRatio / 2.0f);
float B = 1.0f / tan(FieldOfView / 2.0f);
// camera frustum face normals
vec3 normal_L = normalize(vec3(-A, 0, 1));
vec3 normal_R = normalize(vec3(+A, 0, 1));
vec3 normal_T = normalize(vec3(0, +B, 1));
vec3 normal_B = normalize(vec3(0, -B, 1));
// distances of bounding sphere to camera frustum faces
float distance_L = dot(position, normal_L);
float distance_R = dot(position, normal_R);
float distance_T = dot(position, normal_T);
float distance_B = dot(position, normal_B);
// cull invisible objects
bool visible = false;
if (distance_L > radius)
return;
if (distance_R > radius)
return;
if (distance_T > radius)
return;
if (distance_B > radius)
return;
visible = true;
```

i use a bounding sphere for every mesh, transform it into view/eye space, and check if the frustum planes exclude the bounding sphere entirely … if yes, i dont have to draw the mesh