#12975 - twillinx - Tue Dec 02, 2003 10:35 pm
Ok, I'm currently doing a little test were I control a sprite with a sinuscurve, the more I press A button the higher the sinus gets. When I release a button the sprite should move along the same tangent (Don't know if thats the english word for it though. :)) I'll try to explain a little better; when I'm not touching either the A nor the B button the sprite should move along in a straight line from where the sinus ends.
But when the value is between 0 and 1 the sprite doesnt move in the Y-axis, how should I fix this? My guess is that it doesnt work all that good when the value is between 2 and 3 ... and so on either. :D
ship.y-=(int)Momentum;
This works great when I use the (int)blahblah-command during the sinuscalculations and with a 2nd degree-calculation but when its a fixed value; like momentum=0.8 then it doesn't work all of a sudden.
I hope somebody gets through all my ranting and can help me with this problem. Thanks.
#12981 - sajiimori - Tue Dec 02, 2003 11:26 pm
Well, you didn't provide any code, so we can only guess what you're actually doing. I suppose Momentum is some sort of floating point value. When you cast a float or double to an int, it just drops the fractional portion, so obviously a value of 0.8 will round down to 0.
Anyway, you shouldn't be using floating point values on GBA because the CPU doesn't support them (so they have to be emulated).
#13003 - twillinx - Wed Dec 03, 2003 10:38 am
I'm just testing it out right now, I'll probably put it in an array when I know exactly how everything will work out and with what values.
I didn't wanna embaress myself with the code but you leave me no choice;
value+=0.15;
konvert=xstart-(sin(1)*value);
sinus=(int)konvert;
ship.y=sinus;
Here I use the (int) and it looks exactly as I want it to.
If I wan't the ship to continue on in a straight line (according to the current value) when releasing the buttons, how will I solve that? The only idea I got right now is another curve, one that never tops, but there should be a simpler and better solution, I hope.
#13005 - yaustar - Wed Dec 03, 2003 12:59 pm
Try using fix point maths instead. It is highly recommended not to use float numbers as it is very slow
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#13006 - evil saltine - Wed Dec 03, 2003 1:22 pm
| Quote: |
| If I wan't the ship to continue on in a straight line (according to the current value) when releasing the buttons, how will I solve that? The only idea I got right now is another curve, one that never tops, but there should be a simpler and better solution, I hope. |
What path is the sprite making on the screen? Is it moving up and down or in a sinusoidal path?
| Code: |
| konvert=xstart-(sin(1)*value); |
I don't understand this line, it looks like you're multiplying 'value' by a constant, but if it works it's probably what you wanted.. I dunno.
#13011 - tepples - Wed Dec 03, 2003 2:55 pm
| twillinx wrote: |
| If I wan't the ship to continue on in a straight line (according to the current value) when releasing the buttons, how will I solve that? |
First read up on fixed-point arithmetic. Then take the current position, in fixed-point, and subtract the previous position, also in fixed-point. This gives you a velocity in fixed-point; add it every frame to the position of the sprite in question.
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