Physics - Simulation World Scaling to Sim scale.

Another question for the gurus... In most Sim I've seen you translate the cars velocity vectors in the Worldspace velocity vectors (or some such thing). Then these World velocity vectors get added to positional co-ordinates. car_world_pos += car_world_velocity * delta_t; Now is it ok to scale your Sim by doing this.... scale_factor = 10; //(depends on size of model) car_world_pos += car_world_velocity * delta_t * scale_factor; It's only the "Position" I scale nothing else, it seems to work ok, but it appears that the scale_factor value has to match the car model size. In my case, scale_factor = 20 to match my model size. (I'm using A4 Game_Studio & there are min/max limits on sizes of things.)

I can't think of a reason off the top of my head why this wouldn't work just fine....? Todd Wasson --- Performance Simulations Drag Racing and Top Speed Prediction Software http://PerformanceSimulations.Com My little car sim screenshots: http://performancesimulations.com/scnshot4.htm

[email hidden] (J. Todd Wasson) wrote in message news:<[email hidden]>...

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> I can't think of a reason off the top of my head why this wouldn't work just > fine....? > > > Todd Wasson > --- > Performance Simulations > Drag Racing and Top Speed Prediction > Software > http://PerformanceSimulations.Com > > My little car sim screenshots: > http://performancesimulations.com/scnshot4.htm

Thanks Todd, I hoped as much but was unsure if the rotations needed any adjusting...

That should be fine - works in my sim :) Al Steve Hovelroud <[email hidden]> wrote in message news:[email hidden]...

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> Another question for the gurus... > > In most Sim I've seen you translate the cars velocity vectors in the > Worldspace velocity vectors (or some such thing). Then these World > velocity vectors get added to positional co-ordinates. > > car_world_pos += car_world_velocity * delta_t; > > Now is it ok to scale your Sim by doing this.... > > > scale_factor = 10; file://(depends on size of model) > car_world_pos += car_world_velocity * delta_t * scale_factor; > > It's only the "Position" I scale nothing else, it seems to work ok, > but it appears that the scale_factor value has to match the car model > size. In my case, scale_factor = 20 to match my model size. (I'm using > A4 Game_Studio & there are min/max limits on sizes of things.)

On 9 May 2002 16:19:33 -0700, [email hidden] (Steve Hovelroud) wrote:

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>Another question for the gurus... > >In most Sim I've seen you translate the cars velocity vectors in the >Worldspace velocity vectors (or some such thing). Then these World >velocity vectors get added to positional co-ordinates. > > car_world_pos += car_world_velocity * delta_t; > >Now is it ok to scale your Sim by doing this.... > > > scale_factor = 10; //(depends on size of model) > car_world_pos += car_world_velocity * delta_t * scale_factor; > >It's only the "Position" I scale nothing else, it seems to work ok, >but it appears that the scale_factor value has to match the car model >size. In my case, scale_factor = 20 to match my model size. (I'm using >A4 Game_Studio & there are min/max limits on sizes of things.)

It's probably better to try and scale your model (if A4 Game_Studio is a modeling package). If you program a sim, keeping units to something you can relate to is quite important, although mathematically it shouldn't make a difference. That's why US people stick to pounds, and here in Europe we stick to kilograms. And that's why with the new Euro everybody here spends too much money (it's worth more than twice as much as the old guilder, but doesn't feel like that). ;-) Ruud van Gaal Free car sim: http://www.racer.nl/ Pencil art : http://www.marketgraph.nl/gallery/

On Fri, 10 May 2002 17:28:20 GMT, [email hidden] (Ruud van Gaal) wrote: >It's probably better to try and scale your model (if A4 Game_Studio is >a modeling package). If you program a sim, keeping units to something >you can relate to is quite important, although mathematically it >shouldn't make a difference. I agree. It definitely makes a difference in world construction, especially if you ever plan to have more than 1 artist on the project. The cost in iteration, communication, and wasted work is enormous if you don't use a standard scale.

[email hidden] (Joe62) wrote in message news:<[email hidden]>...

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> On Fri, 10 May 2002 17:28:20 GMT, [email hidden] (Ruud van Gaal) > wrote: > > >It's probably better to try and scale your model (if A4 Game_Studio is > >a modeling package). If you program a sim, keeping units to something > >you can relate to is quite important, although mathematically it > >shouldn't make a difference. > > I agree. It definitely makes a difference in world construction, > especially if you ever plan to have more than 1 artist on the project. > The cost in iteration, communication, and wasted work is enormous if > you don't use a standard scale.

The problem is that with GameStudio there is a maximum limit on the world size, so to make the world appear bigger, you make the car smaller. How small?? Well, I try to figure out what the smallest object in my world will be, create it the smallest I can , then scale everything from here. As I'm the only one doing the project, it's just me who has to worry about the size of things. I agree it would be nice to have things real-type-scale but maybe next time... Aussies of my era are fully conversant with both metric & imperial measurements but who wouldn't love metric ;) .

On 12 May 2002 15:31:08 -0700, [email hidden] (Steve Hovelroud) wrote:

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>[email hidden] (Joe62) wrote in message news:<[email hidden]>... >> On Fri, 10 May 2002 17:28:20 GMT, [email hidden] (Ruud van Gaal) >> wrote: >> >> >It's probably better to try and scale your model (if A4 Game_Studio is >> >a modeling package). If you program a sim, keeping units to something >> >you can relate to is quite important, although mathematically it >> >shouldn't make a difference. >> >> I agree. It definitely makes a difference in world construction, >> especially if you ever plan to have more than 1 artist on the project. >> The cost in iteration, communication, and wasted work is enormous if >> you don't use a standard scale. > >The problem is that with GameStudio there is a maximum limit on the >world size, so to make the world appear bigger, you make the car >smaller. > >How small?? > >Well, I try to figure out what the smallest object in my world will >be, create it the smallest I can , then scale everything from here.

I'd stick to scalings of 10, 100 etc, so you can easily chuck the comma around to get at real readings. Using other scales only makes it worse; like going from pounds to N, you quickly scale the wrong way without knowing. :) Ruud van Gaal Free car sim: http://www.racer.nl/ Pencil art : http://www.marketgraph.nl/gallery/

On 12 May 2002 15:31:08 -0700, [email hidden] (Steve Hovelroud) wrote: ... >Well, I try to figure out what the smallest object in my world will >be, create it the smallest I can , then scale everything from here. As an interesting side-note; Quake3 still uses funny units. (in the MD3 format for example). A remainder from Doom, or even Castle Wolfenstein (the old one), where fixed point ruled. Too bad it's still in there, because it is really is something you want to abstract yourself from. Enough trouble apart from units. Ruud van Gaal Free car sim: http://www.racer.nl/ Pencil art : http://www.marketgraph.nl/gallery/

On 12 May 2002 15:31:08 -0700, [email hidden] (Steve Hovelroud) wrote: >Well, I try to figure out what the smallest object in my world will >be, create it the smallest I can , then scale everything from here. As >I'm the only one doing the project, it's just me who has to worry >about the size of things. I agree it would be nice to have things >real-type-scale but maybe next time... It's more important to have STANDARD sizes than REAL sizes. In other words, there's nothing wrong with a rule that says "In this world 1 cm = 1 meter in the real world". An artist can easily figure out how they are suppoosed to build things. At least, they can as long as their not in some backwards, Luddite country that uses the Imperial measurement system!