Well **** me. I missed the second "+ UTIL_SharedRandomFloat( shared_rand + iShot, -0.5, 0.5 )" in the goldsrc method - which takes it back up to +/-1 max range.
At least I know a) the code better and b) not to trust my math :^) Quoting Tim Holt <[EMAIL PROTECTED]>: > Answering my own question a bit maybe. Someone check my math on this? I may > have missed something... > > If you go with straight default values, you have... > > bias = 1.0; > shotBiasMin = -1.0; > shotBiasMax = 1.0; > > Applying those values to the forumula below, you get > > shotBias = ((1.0 - -1.0) * 1.0) + -1.0 > = ((2.0) * 1.0) + -1.0 > = 1.0 > flatness = 1.0 * 0.5 > = 0.5 > > Now - the random number generators use that flatness value, and essentially > are > going to be cranking out values of X and Y that will vary from -1 to +1. And > this is where it really changes from GoldSrc. GoldSrc calculates a random > number from -0.5 to +0.5. Meaning GoldSrc has a shot pattern that's HALF THE > SIZE of Source, if I did my math right. Which means (again if I did this > right) you need to make your vecSpread be half the size in Source that it was > in GoldSrc to get the same accuracy. > > The other difference is the while loop. The while look in the Source version > keeps all points inside of a circle, whereas the GoldSrc version ends up > creating a distribution of points in a square. > > It's worth noting that an alternate way to calculate a random point in a > circle > without the randomness would be as follows... > > float x, y, r, theta; > > r = RandomFloat(0, 1); > theta = RandomFloat (0, 2_PI); > x = sqrt(r) * cos(theta); > y = sqrt(r) * sin(theta); > > More trig, less looping until you get a good number. > > This is from http://mathworld.wolfram.com/DiskPointPicking.html > > > > > > Woops - hit send button while editing - here's the right one... > > > > > > I was looking at the base code that calculates bullet "cone of fire" or > > randomness in Source today, and comparing it with the calculation method in > > GoldSrc (HL1). They are different. I'm curious if anyone could help me > > grok the differences, and just what the effect would be for bullet spread. > > > > > > First, here's the code in shot_manipulator.h that Source uses... > > > > > if ( bias > 1.0 ) > > > bias = 1.0; > > > else if ( bias < 0.0 ) > > > bias = 0.0; > > > > > > float shotBiasMin = ai_shot_bias_min.GetFloat(); > > > float shotBiasMax = ai_shot_bias_max.GetFloat(); > > > > > > // 1.0 gaussian, 0.0 is flat, -1.0 is inverse gaussian > > > float shotBias = ( ( shotBiasMax - shotBiasMin ) * bias ) + shotBiasMin; > > > > > > float flatness = ( fabsf(shotBias) * 0.5 ); > > > > > > do > > > { > > > x = random->RandomFloat(-1,1) * flatness > > > + random->RandomFloat(-1,1) * (1 - flatness); > > > y = random->RandomFloat(-1,1) * flatness > > > + random->RandomFloat(-1,1) * (1 - flatness); > > > if ( shotBias < 0 ) > > > { > > > x = ( x >= 0 ) ? 1.0 - x : -1.0 - x; > > > y = ( y >= 0 ) ? 1.0 - y : -1.0 - y; > > > } > > > z = x*x+y*y; > > > } while (z > 1); > > > > > > m_vecResult = m_vecShotDirection > > > + x * vecSpread.x * m_vecRight > > > + y * vecSpread.y * m_vecUp; > > > > > > Here is the (I think) equivalent code that GoldSrc (HL1) uses... > > > > > x = UTIL_SharedRandomFloat( shared_rand + iShot, -0.5, 0.5 ) > > > + UTIL_SharedRandomFloat( shared_rand + ( 1 + iShot ) , -0.5, 0.5 ); > > > y = UTIL_SharedRandomFloat( shared_rand + ( 2 + iShot ), -0.5, 0.5 ) > > > + UTIL_SharedRandomFloat( shared_rand + ( 3 + iShot ), -0.5, 0.5 ); > > > z = x * x + y * y; > > > > > > Vector vecDir = vecDirShooting > > > + x * vecSpread.x * vecRight > > > + y * vecSpread.y * vecUp; > > > > > > So you can see how the X and Y are calculated differently in the two. > Source > > has a "bias" value that influences how it works. Source also loops until > you > > get an X and Y that lay inside of a circle (that while loop on Z) but > GoldSrc > > doesn't. > > > > So basically, what will the difference be between these two systems? What > > will > > the bias value's influece be on the randomness? > > > > I actually started looking into this because I want to code a weighted > > randomness - with more points concentrated in the middle. Take a look at > > http://mathworld.wolfram.com/DiskPointPicking.html for an article about how > > NOT > > to do this (ironically). > > > > > > _______________________________________________ > > To unsubscribe, edit your list preferences, or view the list archives, > please > > visit: > > http://list.valvesoftware.com/mailman/listinfo/hlcoders > > > > > > > _______________________________________________ To unsubscribe, edit your list preferences, or view the list archives, please visit: http://list.valvesoftware.com/mailman/listinfo/hlcoders
