For what it's worth I think realistic tire smoke is a little more important than the orange peel effect or something in a similar capacity. Why make the visuals so pretty that you can't even have decent smoke effects? FM4's smoke effects are far better... yes, that's actually embarrassing to admit.
The orange peel effect on a cars paint wont do much in terms of a graphical sense, as it is just a material based texture. So once it is loaded up, it wont be using much of the system resources.
Tire smoke on the other hand, that is often done with a texture applied to a particle effect emitter. The same as the dust when one drives off the tarmac. Particle effects are a massive resource hog, and they will have an "and/or" instance applied to them to call them into the visuals or not. So this takes CPU resources to call them in, and both CPU/GPU resources to render them. They can get quite intensive, especially in a real time render situation as in a video game environment. Even the reflections/refractions in the cars paint itself will have more of an effect on the CPU and GPU then the orange peel effect
Look at it this way. I could model a car in the same detail T10 do, give it a paint material with orange peel. But have the reflections turned off in my render settings. I could render that up in say 20 minutes with a basic scene and lighting, say a corner of a race track. This could be using say 50% of my total CPU and/or 10% of my GPU (if I have GPU rendering turned on)
Then I could add on the reflections/refractions of the car paint, and this could see the render time increase to 40 minutes+. usually with an increase to the resources used, say like 65%CPU and/or 15% GPU. Add in HDR to it all, could see the render times increase a further 5+ minutes.
Then say I make the car look like it is drifting around the corner in question. So I would add a particle emitter, and add a suitable material based texture to it. And then I would go about using frames from say 0 to 100, to find what I perceive as the perfect point for the particle based tire smoke. Render that up, and you could then see the render time increase a further 30+ minutes, with 90+ CPU usage, and/or 30+GPU usage. (GPU is often used less when messing with a 3d application for rendering)
Obviously the timings I am using are hypothetical, but you should be able to see my point. Going from a very basic scene, to one with much better lighting. with reflections and HDR, and tire smoke. You could see your render times triple and more. Something at the very basic level which rendered up in 20 minutes, could take hours once all the effects are applied.
Obviously the renderer built into Forza (and other games), is a real time based one. The effects are called into existence by the games code, and are turned off by the games code. This has to happen very quickly as well. But the things such as the textures are preloaded in a game. Things like particle emitters though, these are only called into the game when needed.
The best way to prove this point, would be to load up FM5 (or FM4 if you still dont have FM5/X1). And then just sit in one spot on the track spinning the tires. After a few seconds, you will notice the frames have definitely gone below 60FPS. Even with the smoke effects not to your liking, they are still having an effect on what the system can do. So imagine what would happen to FM6 if T10 suddenly added night racing with a basic form of volumetric based lighting for the car lights, better tire smoke and dirt effects. And then on top of that, add rain into the mix. If they are not careful in their implementations, FM6 would be a locked 30FPS game at the least (think driveclub). Or will be an unlocked 60FPS game, where the FPS could tank as soon as you try to race in the rain, and at night.
You also have to remember that on the track in forza, the physics are always running as well. and this is using the CPU all the time for the calculations needed to make them run. So around half the total CPU power of the X1 (or 360 for FM4) will be used solely by the physics alone while on track.
This is why T10 have not added these things in the motorsport series yet (baring pacific shipyards in FM1 for night racing, and the reason they have not done it again since FM1). Unless they can add all those things without tanking the framerate, they will not do it. And for this reason, I am not going to get hyped up over those effects just because FH2 has them. I will wait till T10 say if we have those things or not. If they have added night and/or weather this time around for FM6, they will show it off at E3. As it would be the biggest selling point for FM6 by far.
