commit 309255000265069b2c667f7a0845c697dc6d3333 Author: Leszek Koltunski Date: Sun Jul 17 22:27:41 2016 +0100 Fix for Bug #18: DISTORT effect: disappearing triangles diff --git a/src/main/res/raw/main_vertex_shader.glsl b/src/main/res/raw/main_vertex_shader.glsl index 4e32e11..ec6ef9d 100644 --- a/src/main/res/raw/main_vertex_shader.glsl +++ b/src/main/res/raw/main_vertex_shader.glsl @@ -236,7 +236,8 @@ void deform(in int effect, inout vec4 v) // Solution: // 1. Decompose the V into two subcomponents, one parallel to SX and another perpendicular. // 2. Convince yourself (draw!) that the perpendicular component has no effect on normals. -// 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) +// 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) // 4. that in turn leaves the x and y parts of the normal unchanged and multiplies the z component by a! // // |Vpar| = (u_dVx[i]*dx - u_dVy[i]*dy) / sqrt(ps_sq) = (Vx*dx-Vy*dy)/ sqrt(ps_sq) (-Vy because y is inverted) @@ -258,8 +259,8 @@ void deform(in int effect, inout vec4 v) // so finally -|PS|/f'(|PX|) = -ps_sq/ (6uz*d*(1-d)^2) // // Case 3: -// 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 -// so this produces a fuller, thicker bubble! +// 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, +// f(0.5)=0.7 and f'(t)= t(t-1)^2 >=0 for t>=0 so this produces a fuller, thicker bubble! // then -|PS|/f'(|PX|) = (-|PS|*|SX)) / (12uz*d*(d-1)^2) but |PS|*|SX| = ps_sq/(1-d) (see above!) // so finally -|PS|/f'(|PX|) = -ps_sq/ (12uz*d*(1-d)^3) // @@ -269,8 +270,8 @@ void deform(in int effect, inout vec4 v) // 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 // add up the first and second components. // -// 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. -// (a is the horizontal part) +// 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. (a is the horizontal part) void distort(in int effect, inout vec4 v, inout vec4 n) { @@ -278,17 +279,18 @@ void distort(in int effect, inout vec4 v, inout vec4 n) vec2 ps = point-v.xy; float d = degree(vUniforms[effect+1],point,ps); vec2 w = vec2(vUniforms[effect].x, -vUniforms[effect].y); - float dt = dot(ps,ps); - float uz = vUniforms[effect].z; // height of the bubble - - //v.z += uz*d; // cone - //b = -(uz*(1.0-d)) / (dt + (1.0-d)*dot(w,ps) + (sign(dt)-1.0) ); // + float uz = vUniforms[effect].z; // height of the bubble + float denominator = dot(ps+(1.0-d)*w,ps); + float one_over_denom = 1.0/(denominator+0.001*(1.0-sign(denominator))); // = denominator==0 ? 1000:1/denominator; + + //v.z += uz*d; // cone + //b = -(uz*(1.0-d))*one_over_denom; // - //v.z += uz*d*d*(3.0-2.0*d); // thin bubble - //b = -(6.0*uz*d*(1.0-d)*(1.0-d)) / (dt + (1.0-d)*dot(w,ps) + (sign(dt)-1.0) ); // + //v.z += uz*d*d*(3.0-2.0*d); // thin bubble + //b = -(6.0*uz*d*(1.0-d)*(1.0-d))*one_over_denom; // - v.z += uz*d*d*(3.0*d*d -8.0*d +6.0); // thick bubble - 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) + v.z += uz*d*d*(3.0*d*d -8.0*d +6.0); // thick bubble + float b = -(12.0*uz*d*(1.0-d)*(1.0-d)*(1.0-d))*one_over_denom; // v.xy += d*w; n.xy += b*ps;