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author | Lars Knoll <lars.knoll@nokia.com> | 2009-03-23 09:34:13 (GMT) |
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committer | Simon Hausmann <simon.hausmann@nokia.com> | 2009-03-23 09:34:13 (GMT) |
commit | 67ad0519fd165acee4a4d2a94fa502e9e4847bd0 (patch) | |
tree | 1dbf50b3dff8d5ca7e9344733968c72704eb15ff /src/opengl/util/ellipse_functions.glsl | |
download | Qt-67ad0519fd165acee4a4d2a94fa502e9e4847bd0.zip Qt-67ad0519fd165acee4a4d2a94fa502e9e4847bd0.tar.gz Qt-67ad0519fd165acee4a4d2a94fa502e9e4847bd0.tar.bz2 |
Long live Qt!
Diffstat (limited to 'src/opengl/util/ellipse_functions.glsl')
-rw-r--r-- | src/opengl/util/ellipse_functions.glsl | 63 |
1 files changed, 63 insertions, 0 deletions
diff --git a/src/opengl/util/ellipse_functions.glsl b/src/opengl/util/ellipse_functions.glsl new file mode 100644 index 0000000..eed18e8 --- /dev/null +++ b/src/opengl/util/ellipse_functions.glsl @@ -0,0 +1,63 @@ +uniform vec3 inv_matrix_m0; +uniform vec3 inv_matrix_m1; +uniform vec3 inv_matrix_m2; + +uniform vec2 ellipse_offset; + +float ellipse() +{ + vec2 st = gl_TexCoord[0].st; + + if (dot(st, st) > 1) + discard; + + return 1.0; +} + +// ellipse equation + +// s^2/a^2 + t^2/b^2 = 1 +// +// implicit equation: +// g(s,t) = 1 - s^2/r_s^2 - t^2/r_t^2 + +// distance from ellipse: +// grad = [dg/dx dg/dy] +// d(s, t) ~= g(s, t) / |grad| + +// dg/dx = dg/ds * ds/dx + dg/dt * dt/dx +// dg/dy = dg/ds * ds/dy + dg/dt * dt/dy + +float ellipse_aa() +{ + mat3 mat; + + mat[0] = inv_matrix_m0; + mat[1] = inv_matrix_m1; + mat[2] = inv_matrix_m2; + + vec3 hcoords = mat * vec3(gl_FragCoord.xy + ellipse_offset, 1); + float inv_w = 1.0 / hcoords.z; + vec2 st = hcoords.xy * inv_w; + + vec4 xy = vec4(mat[0].xy, mat[1].xy); + vec2 h = vec2(mat[0].z, mat[1].z); + + vec4 dstdxy = (xy.xzyw - h.xyxy * st.xxyy) * inv_w; + + //dstdxy.x = (mat[0].x - mat[0].z * st.x) * inv_w; // ds/dx + //dstdxy.y = (mat[1].x - mat[1].z * st.x) * inv_w; // ds/dy + //dstdxy.z = (mat[0].y - mat[0].z * st.y) * inv_w; // dt/dx + //dstdxy.w = (mat[1].y - mat[1].z * st.y) * inv_w; // dt/dy + + vec2 inv_r = gl_TexCoord[0].xy; + vec2 n = st * inv_r; + float g = 1.0 - dot(n, n); + + vec2 dgdst = -2.0 * n * inv_r; + + vec2 grad = vec2(dot(dgdst, dstdxy.xz), + dot(dgdst, dstdxy.yw)); + + return smoothstep(-0.5, 0.5, g * inversesqrt(dot(grad, grad))); +} |