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Revision 30925500

Added by Leszek Koltunski almost 8 years ago

Fix for Bug #18: DISTORT effect: disappearing triangles

View differences:

src/main/res/raw/main_vertex_shader.glsl
236 236 
// Solution:
237 237 
// 1. Decompose the V into two subcomponents, one parallel to SX and another perpendicular.
238 238 
// 2. Convince yourself (draw!) that the perpendicular component has no effect on normals.
239 
// 3. The parallel component changes the length of |SX| by the factor of a=(|SX|-|Vpar|)/|SX| (where the length can be negative depending on the direction)
239 
// 3. The parallel component changes the length of |SX| by the factor of a=(|SX|-|Vpar|)/|SX| (where the length
240 
//    can be negative depending on the direction)
240 241 
// 4. that in turn leaves the x and y parts of the normal unchanged and multiplies the z component by a!
241 242 
//
242 243 
// |Vpar| = (u_dVx[i]*dx - u_dVy[i]*dy) / sqrt(ps_sq) = (Vx*dx-Vy*dy)/ sqrt(ps_sq)  (-Vy because y is inverted)
......
258 259 
// so finally -|PS|/f'(|PX|) = -ps_sq/ (6uz*d*(1-d)^2)
259 260 
//
260 261 
// Case 3:
261 
// f(t) = 3t^4-8t^3+6t^2 would be better as this safisfies f(0)=0, f'(0)=0, f'(1)=0, f(1)=1 and f(0.5)=0.7 and f'(t)= t(t-1)^2 >=0 for t>=0
262 
// so this produces a fuller, thicker bubble!
262 
// f(t) = 3t^4-8t^3+6t^2 would be better as this safisfies f(0)=0, f'(0)=0, f'(1)=0, f(1)=1,
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// f(0.5)=0.7 and f'(t)= t(t-1)^2 >=0 for t>=0 so this produces a fuller, thicker bubble!
263 264 
// then -|PS|/f'(|PX|) = (-|PS|*|SX)) / (12uz*d*(d-1)^2) but |PS|*|SX| = ps_sq/(1-d) (see above!)
264 265 
// so finally -|PS|/f'(|PX|) = -ps_sq/ (12uz*d*(1-d)^3)
265 266 
//
......
269 270 
// then the normal to g = f1+f2 is simply given by (f1x+f2x,f1y+f2y,1), i.e. if the third component is 1, then we can simply
270 271 
// add up the first and second components.
271 272 
//
272 
// Thus we actually want to compute N(v.x,v.y) = a*(-(dx/|PS|)*f'(|PX|), -(dy/|PS|)*f'(|PX|), 1) and keep adding the first two components.
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// (a is the horizontal part)
273 
// Thus we actually want to compute N(v.x,v.y) = a*(-(dx/|PS|)*f'(|PX|), -(dy/|PS|)*f'(|PX|), 1) and keep adding
274 
// the first two components. (a is the horizontal part)
274 275
275 276 
void distort(in int effect, inout vec4 v, inout vec4 n)
276 277 
  {
......
278 279 
  vec2 ps = point-v.xy;
279 280 
  float d = degree(vUniforms[effect+1],point,ps);
280 281 
  vec2 w = vec2(vUniforms[effect].x, -vUniforms[effect].y);
281 
  float dt = dot(ps,ps);
282 
  float uz = vUniforms[effect].z; // height of the bubble
283
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  //v.z += uz*d;                                                                                // cone
285 
  //b = -(uz*(1.0-d)) / (dt + (1.0-d)*dot(w,ps) + (sign(dt)-1.0) );                             //
282 
  float uz = vUniforms[effect].z;                                         // height of the bubble
283 
  float denominator = dot(ps+(1.0-d)*w,ps);
284 
  float one_over_denom = 1.0/(denominator+0.001*(1.0-sign(denominator))); // = denominator==0 ? 1000:1/denominator;
285 

  		




  
  286
  
    
  //v.z += uz*d;                                                          // cone


  		




  
  287
  
    
  //b = -(uz*(1.0-d))*one_over_denom;                                     //


  		




  286
  288
  
    
        


  		




  287
  
  
    
  //v.z += uz*d*d*(3.0-2.0*d);                                                                  // thin bubble


  		




  288
  
  
    
  //b = -(6.0*uz*d*(1.0-d)*(1.0-d)) / (dt + (1.0-d)*dot(w,ps) + (sign(dt)-1.0) );               //


  		




  
  289
  
    
  //v.z += uz*d*d*(3.0-2.0*d);                                            // thin bubble


  		




  
  290
  
    
  //b = -(6.0*uz*d*(1.0-d)*(1.0-d))*one_over_denom;                       //


  		




  289
  291
  
    
        


  		




  290
  
  
    
  v.z += uz*d*d*(3.0*d*d -8.0*d +6.0);                                                          // thick bubble


  		




  291
  
  
    
  float b = -(12.0*uz*d*(1.0-d)*(1.0-d)*(1.0-d)) / (dt + (1.0-d)*dot(w,ps) + (sign(dt)-1.0) );  // the last part - (sign-1) is to avoid b being a NaN when ps=(0,0)


  		




  
  292
  
    
  v.z += uz*d*d*(3.0*d*d -8.0*d +6.0);                                    // thick bubble


  		




  
  293
  
    
  float b = -(12.0*uz*d*(1.0-d)*(1.0-d)*(1.0-d))*one_over_denom;          //


  		




  292
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  293
  295
  
    
  v.xy += d*w;


  		




  294
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  n.xy += b*ps;


  		












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