UOIT Game Dev - Development Blog 8 - The Portal Challenge

So this week instead of another lecture, we were given a challenge. And that challenge was to create functioning portals from the game Portal in 1 hour and 30 minutes. This was a very interesting challenge since prior to that class I wasn't able to successfully render FBO textures to 3D quads.

So we formed a group of 4 and began to brainstorm thoughts. First thing was to get an actual quad in there, so all I did was model a plane in Maya and imported it into my game. Then we tried to render "something" onto that plane, we wanted to have the quad display the scene from our camera's perspective.

What I did next was use my HDR shader class to render the scene to an FBO texture. I drew the scene in the first pass to get the scene texture, then render it again with the quad's texture replaced with the FBO texture.

What happened next was weird. Although we were able to render something on the quad, the texture looked really stretched, all we could see were lines of colour. It took us about 10 minutes to figure out what was wrong and it turned out to be the way we declared the texture parameters for our FBO texture. I replaced the parameters with the same ones we used to load our texture for the models and it worked flawlessly.

So with that out of the way we wanted 2 portals with each of them displaying the scene. This was really simple as we simply repeated step1.

Now how do we make it so one portal displays what ever the other portal is looking at? hmm....
Well this requires more passes and saved camera transformations.

We saved the initial camera matrix prior to rendering, took our camera and set it up on Portal A's position and view then rendered the scene. We did the same with Portal B and now there are 2 scene textures available rendered at 2 different locations.

All we did for the final render pass was apply Portal B's scene texture to Portal A and vice versa.
This pretty much did the trick, however we still didn't have parallax working so it seemed strange to have the portal display a static image.

But luckily this was an easy fix, we simply took the directions from the camera to each of the portal positions, found out the angle of the direction, then rotated it about 180 degrees to face the player. This was the final tweak that allowed us to come up with a functioning portal (other than the actual physics part lol).

On the development side, I've finally decided to implement tangent space normal mapping. It added a lot more detail to our map and looks pretty nice. Also, Gimp's normal mapping plugin is amazing and pretty much allowed me to make normal maps in less than a minute. 

Well, that's all for this week. Our game is near beta, we should have all of the functionality done by next week.