Greetings. In short: I seek informations about inclined planes in 3D (importante!). Do you know any articles or pages in the internet? Is anyone out there offering to share his knowledge? Thanks

Inclined ????
the equation of plane states as follow ax+by+cz+d=0
a,b,c is the vector , you should find a vector orientating with that to incline your plane , but you have to use quaterinons
anyway did you know that having 3 points in space you can describe fully a plane ?

I mean inclined planes in physics, forces down the plane, friction, etc.

Inclined planes in physics is a massive topic, and if you wanted to do it properly you would have to have all sorts of stuff like friction coefficients and you would have to resolve forces and use Newton''s 2nd law to find accelleration. Then, you would have to apply the accelleration to the object and all sorts of other stuff - the guts of a professional physics engine which would require a lot of programming plus a lot of processing power.

Hope that at least give you somewhere to start,
Andrew.

well if you left out friction then it wouldnt be to difficult

Diakon-

I know very little about 3D programming, but I''d be glad to give you a hand with the physics. How much physics do you currently know? Let me know what you''ve heard of:

-force vectors
-friction coefficients
-F=ma
-normal force (normal = perpendicular, not "regular")
-resolving vectors using trig
-free body diagrams

Like adpeace said, doing this properly is going to be pretty complex. What exactly are you trying to do?

Good luck,
Rob

I want to make my player slip down a slope if the inclined plane has a big angle (friction and slope acceleration).

OK. First decide if they''re going to slip at all.

The friction the player encounters is based on three things: (1) the angle of the plane, (2) the players weight (which is proportional to their mass), and (3) the friction coefficient between the player''s shoes and the floor. You have to consider friction or else they would always slide down every plane.

(1) I assume you can figure this out yourself (because I can''t).
(2) If only players are doing the sliding and all players are the same, then this is not really important. But if other things are sliding, too, then you need to assign relative "weights" to them. (If player weighs 1, big steel box weighs 10, or whatever.)
(3) This depends on the materials. For example, a rubber boot will stick to a metal suface better than a steel box. Higher numbers = better sticking = more friction. Go to this site for some actual experimental values, but again if only players are slipping on the same material, don''t worry about it.

Now for the math. The object will slip if fc*W*cos(angle) < W*sin(angle), where fc is the friction coefficient and W is the weight. You''ll notice that there is an angle where thay are equal - anything above it will cause slipping, anything below will not. Just figure out the angle for all of you combinations of fc and W once and remember it. Since fc and W are pretty arbitrary, you''ll need to experiment a lot to make it realistic.

Next decide how fast they will slip. Their acceleration is proportional to sin(angle), so the bigger the angle, the faster they slip (common sense). Of course, since they''re accelerating, their speed will increase with time. Since your weights are largely arbitrary, then the actual acceleration is, too - as long as it is proportional to sin(angle). The object''s velocity at any one point will be acceleration*time (assuming they start sliding at time = 0).

Now, I''m all for realism, but this sounds like a lot to actually implement. Especially since most of the physics is invisible to the end result anyway. It''s going to boil down to finding the angle where slipping starts and knowing that every angle above it (made of the same material) is going to cause slipping, too. It really depends on how fancy you want to get. And I didn''t even think of what happens when the player tries to go up a slippery slope...whew. I guess that means that they would have to walk (or run, whatever) with a force of more than W*sin(angle) - fc*W*cos(angle). Then you''d have to figure out what force they run at. Oh well, here''s something to start with. I have no idea how real games do this, this is just what they teach you in physics. I hope it made sense.

Good luck,
Rob