High all,

In a 3D first-person / ego perspective game I've got a simple script that checks whether the player is currently located inside of one of a list of specified coordinate boxes (say, in a room of a list of defined rooms), and execute some shader / post process accordingly.

Now what I would need instead is to check whether what the players currently sees is the inside of one of those coordinate boxes, i.e. he might still be outside but on screen sees only the inside of the box, or vice-versa, looks from within the box to the outside.

I could do such a check either by scripting the engine, or in the responsible post process shader.

How would I achieve this? Any suggestions are welcome.

Thanks for your suggestions, guys

Ok, I've checked the suggestions. It seems that I could do some sort of frustum culling or per-pixel-box-check, but both approaches require a rather ugly set of calculations which I'd like to avoid if there is a simpler way.

What I actually have at the point where I would like to do the check (high-level script on CPU, not GPU side):

• Camera world position
• Camera direction
• Camera FOV
• 2 Box corner world coordinates (left-bottom-front, right-top-back)

What I do not have right away:

• View frustrum definition (near/far plane or say 6 planes defining frustum)
• Any specific pixel information (uv, view space position, depth or the like)

What I would like to calculate:

• Percentage of screen "covered" by box.

Any clues on how to perform such calculation?

Nobody?

I had thought of some check using the view angles between the camera direction and the view vector (direction) to the box's corners or its center point. That way I could for example determine whether a certain point (i.e. corner vertex) is located inside or outside of the screen boundaries, only be checking view angle and distance, thus avoiding the requirement of any world-to-screen-space or whatever matrix calculations.

What do you guys think of such an approach?

What exactly are you trying to do again?

Not sure if you're kidding me, or what's so hard to understand after all my descriptions... but well, OK:

As written in my initial post, I want my host application to decide which (pixel) shader to execute, depending on if the camera's view shows mainly (i.e. high percentage of screen coverage) the inside of an area defined by an (imaginary) cube / box. It is not sufficient to know whether the camera / player is located inside of that cube, but I need to know if what is visible on screen is the inside of that cube.

Think of a cubic area of radioactivity that should cause the execution of some noise post-process effect when the player is inside of or near that area, but only if he's facing / seeing the area.

I do not want to use frustum culling to find the intersection between the view frustum and the box, which would be the "classic" approach for the given task. The main reason for this is that I do not have a near and far plane given in my host app, only the FOV plus by calculation the distance and angle to any point on the map.

I do not want to use Hodgman's idea either because my host app knows crap about any DirectX calls, which would be required for that approach.

So I need some other way to check what the camera currently sees, a way that requires nothing but the things that I actually have in my application, that is as said before:

• Camera world position
• Camera direction
• Camera FOV
• 2 Box corner world coordinates (left-bottom-front, right-top-back)

plus the mentioned functions to calculate the distance and view angle to a given world space point.

Was that clear now? Thanks for any suggestions.

Thank you.