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1 pixel wide lines using OpenGL shaders.

This commit is contained in:
Maciej Suminski 2013-07-16 08:49:12 +02:00
parent 64122ae057
commit 20c86db71f
3 changed files with 89 additions and 56 deletions
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71
common/gal/opengl/opengl_gal.cpp
View File

@ -783,22 +783,23 @@ void OPENGL_GAL::DrawCircle( const VECTOR2D& aCenterPoint, double aRadius )
color4( fillColor.r, fillColor.g, fillColor.b, fillColor.a ); color4( fillColor.r, fillColor.g, fillColor.b, fillColor.a );
/* Draw a triangle that contains the circle, then shade it leaving only the circle. /* Draw a triangle that contains the circle, then shade it leaving only the circle.
Parameters given to setShader are relative coordinates of the triangle's vertices. Parameters given to setShader are indices of the triangle's vertices
(if you want to understand more, check the vertex shader source [shader.vert]).
Shader uses this coordinates to determine if fragments are inside the circle or not. Shader uses this coordinates to determine if fragments are inside the circle or not.
v2 v2
/\ /\
//\\ //\\
v0 /_\/_\ v1 v0 /_\/_\ v1
*/ */
setShader( SHADER_FILLED_CIRCLE, -sqrt( 3.0f ), -1.0f ); setShader( SHADER_FILLED_CIRCLE, 1.0 );
vertex3( aCenterPoint.x - aRadius * sqrt( 3.0f ), // v0 vertex3( aCenterPoint.x - aRadius * sqrt( 3.0f ),
aCenterPoint.y - aRadius, layerDepth ); aCenterPoint.y - aRadius, layerDepth ); // v0
setShader( SHADER_FILLED_CIRCLE, sqrt( 3.0f ), -1.0f ); setShader( SHADER_FILLED_CIRCLE, 2.0 );
vertex3( aCenterPoint.x + aRadius * sqrt( 3.0f ), // v1 vertex3( aCenterPoint.x + aRadius * sqrt( 3.0f ),
aCenterPoint.y - aRadius, layerDepth ); aCenterPoint.y - aRadius, layerDepth ); // v1
setShader( SHADER_FILLED_CIRCLE, 0.0f, 2.0f ); setShader( SHADER_FILLED_CIRCLE, 3.0 );
vertex3( aCenterPoint.x, aCenterPoint.y + aRadius * 2.0f, layerDepth ); // v2 vertex3( aCenterPoint.x, aCenterPoint.y + aRadius * 2.0f, layerDepth ); // v2
} }
@ -807,30 +808,25 @@ void OPENGL_GAL::DrawCircle( const VECTOR2D& aCenterPoint, double aRadius )
color4( strokeColor.r, strokeColor.g, strokeColor.b, strokeColor.a ); color4( strokeColor.r, strokeColor.g, strokeColor.b, strokeColor.a );
/* Draw a triangle that contains the circle, then shade it leaving only the circle. /* Draw a triangle that contains the circle, then shade it leaving only the circle.
Parameters given to setShader are relative coordinates of the triangle's vertices Parameters given to setShader are indices of the triangle's vertices
(if you want to understand more, check the vertex shader source [shader.vert]).
and the line width. Shader uses this coordinates to determine if fragments are inside and the line width. Shader uses this coordinates to determine if fragments are inside
the circle or not. Width parameter has to be passed as a ratio of inner radius the circle or not.
to outer radius.
v2 v2
/\ /\
//\\ //\\
v0 /_\/_\ v1 v0 /_\/_\ v1
*/ */
float outerRadius = aRadius + ( lineWidth / 2.0f ); setShader( SHADER_STROKED_CIRCLE, 1.0, aRadius, lineWidth );
float innerRadius = aRadius - ( lineWidth / 2.0f ); vertex3( aCenterPoint.x - aRadius * sqrt( 3.0f ),
float relWidth = innerRadius / outerRadius; aCenterPoint.y - aRadius, layerDepth ); // v0
setShader( SHADER_STROKED_CIRCLE, -sqrt( 3.0f ), -1.0f, relWidth ); setShader( SHADER_STROKED_CIRCLE, 2.0, aRadius, lineWidth );
vertex3( aCenterPoint.x - outerRadius * sqrt( 3.0f ), // v0 vertex3( aCenterPoint.x + aRadius * sqrt( 3.0f ),
aCenterPoint.y - outerRadius, layerDepth ); aCenterPoint.y - aRadius, layerDepth ); // v1
setShader( SHADER_STROKED_CIRCLE, sqrt( 3.0f ), -1.0f, relWidth ); setShader( SHADER_STROKED_CIRCLE, 3.0, aRadius, lineWidth );
vertex3( aCenterPoint.x + outerRadius * sqrt( 3.0f ), // v1 vertex3( aCenterPoint.x, aCenterPoint.y + aRadius * 2.0f, layerDepth ); // v2
aCenterPoint.y - outerRadius, layerDepth );
setShader( SHADER_STROKED_CIRCLE, 0.0f, 2.0f, relWidth );
vertex3( aCenterPoint.x, // v2
aCenterPoint.y + outerRadius * 2.0f, layerDepth );
} }
return; return;
@ -931,20 +927,21 @@ void OPENGL_GAL::drawFilledSemiCircle( const VECTOR2D& aCenterPoint, double aRad
Rotate( aAngle ); Rotate( aAngle );
/* Draw a triangle that contains the semicircle, then shade it to leave only the semicircle. /* Draw a triangle that contains the semicircle, then shade it to leave only the semicircle.
Parameters given to setShader are relative coordinates of the triangle's vertices. Parameters given to setShader are indices of the triangle's vertices
(if you want to understand more, check the vertex shader source [shader.vert]).
Shader uses this coordinates to determine if fragments are inside the semicircle or not. Shader uses this coordinates to determine if fragments are inside the semicircle or not.
v2 v2
/\ /\
/__\ /__\
v0 //__\\ v1 v0 //__\\ v1
*/ */
setShader( SHADER_FILLED_CIRCLE, -3.0f / sqrt( 3.0f ), 0.0f ); setShader( SHADER_FILLED_CIRCLE, 4.0f );
vertex3( -aRadius * 3.0f / sqrt( 3.0f ), 0.0f, layerDepth ); // v0 vertex3( -aRadius * 3.0f / sqrt( 3.0f ), 0.0f, layerDepth ); // v0
setShader( SHADER_FILLED_CIRCLE, 3.0f / sqrt( 3.0f ), 0.0f ); setShader( SHADER_FILLED_CIRCLE, 5.0f );
vertex3( aRadius * 3.0f / sqrt( 3.0f ), 0.0f, layerDepth ); // v1 vertex3( aRadius * 3.0f / sqrt( 3.0f ), 0.0f, layerDepth ); // v1
setShader( SHADER_FILLED_CIRCLE, 0.0f, 2.0f ); setShader( SHADER_FILLED_CIRCLE, 6.0f );
vertex3( 0.0f, aRadius * 2.0f, layerDepth ); // v2 vertex3( 0.0f, aRadius * 2.0f, layerDepth ); // v2
Restore(); Restore();
@ -973,26 +970,22 @@ void OPENGL_GAL::drawStrokedSemiCircle( const VECTOR2D& aCenterPoint, double aRa
Rotate( aAngle ); Rotate( aAngle );
/* Draw a triangle that contains the semicircle, then shade it to leave only the semicircle. /* Draw a triangle that contains the semicircle, then shade it to leave only the semicircle.
Parameters given to setShader are relative coordinates of the triangle's vertices Parameters given to setShader are indices of the triangle's vertices
and the line width. Shader uses this coordinates to determine if fragments are inside (if you want to understand more, check the vertex shader source [shader.vert]), the
the semicircle or not. Width parameter has to be passed as a ratio of inner radius radius and the line width. Shader uses this coordinates to determine if fragments are
to outer radius. inside the semicircle or not.
v2 v2
/\ /\
/__\ /__\
v0 //__\\ v1 v0 //__\\ v1
*/ */
float outerRadius = aRadius; setShader( SHADER_STROKED_CIRCLE, 4.0f, aRadius, lineWidth );
float innerRadius = aRadius - lineWidth;
float relWidth = innerRadius / outerRadius;
setShader( SHADER_STROKED_CIRCLE, -3.0f / sqrt( 3.0f ), 0.0f, relWidth );
vertex3( -aRadius * 3.0f / sqrt( 3.0f ), 0.0f, layerDepth ); // v0 vertex3( -aRadius * 3.0f / sqrt( 3.0f ), 0.0f, layerDepth ); // v0
setShader( SHADER_STROKED_CIRCLE, 3.0f / sqrt( 3.0f ), 0.0f, relWidth ); setShader( SHADER_STROKED_CIRCLE, 5.0f, aRadius, lineWidth );
vertex3( aRadius * 3.0f / sqrt( 3.0f ), 0.0f, layerDepth ); // v1 vertex3( aRadius * 3.0f / sqrt( 3.0f ), 0.0f, layerDepth ); // v1
setShader( SHADER_STROKED_CIRCLE, 0.0f, 2.0f, relWidth ); setShader( SHADER_STROKED_CIRCLE, 6.0f, aRadius, lineWidth );
vertex3( 0.0f, aRadius * 2.0f, layerDepth ); // v2 vertex3( 0.0f, aRadius * 2.0f, layerDepth ); // v2
Restore(); Restore();

15
common/gal/opengl/shader.frag
View File

@ -32,20 +32,25 @@ const float SHADER_FILLED_CIRCLE = 2.0;
const float SHADER_STROKED_CIRCLE = 3.0; const float SHADER_STROKED_CIRCLE = 3.0;
varying vec4 shaderParams; varying vec4 shaderParams;
varying vec2 circleCoords;
void filledCircle( vec2 aCoord ) void filledCircle( vec2 aCoord )
{ {
if( dot( aCoord, aCoord ) < 1.0 ) if( dot( aCoord, aCoord ) < 1.0f )
gl_FragColor = gl_Color; gl_FragColor = gl_Color;
else else
discard; discard;
} }
void strokedCircle( vec2 aCoord, float aWidth ) void strokedCircle( vec2 aCoord, float aRadius, float aWidth )
{ {
float outerRadius = aRadius;
float innerRadius = aRadius - aWidth;
float relWidth = innerRadius / outerRadius;
if( ( dot( aCoord, aCoord ) < 1.0 ) && if( ( dot( aCoord, aCoord ) < 1.0 ) &&
( dot( aCoord, aCoord ) > aWidth * aWidth ) ) ( dot( aCoord, aCoord ) > relWidth * relWidth ) )
gl_FragColor = gl_Color; gl_FragColor = gl_Color;
else else
discard; discard;
@ -56,11 +61,11 @@ void main()
{ {
if( shaderParams[0] == SHADER_FILLED_CIRCLE ) if( shaderParams[0] == SHADER_FILLED_CIRCLE )
{ {
filledCircle( vec2( shaderParams[1], shaderParams[2] ) ); filledCircle( circleCoords );
} }
else if( shaderParams[0] == SHADER_STROKED_CIRCLE ) else if( shaderParams[0] == SHADER_STROKED_CIRCLE )
{ {
strokedCircle( vec2( shaderParams[1], shaderParams[2] ), shaderParams[3] ); strokedCircle( circleCoords, shaderParams[2], shaderParams[3] );
} }
else else
{ {

39
common/gal/opengl/shader.vert
View File

@ -31,8 +31,12 @@ const float SHADER_LINE = 1.0;
const float SHADER_FILLED_CIRCLE = 2.0; const float SHADER_FILLED_CIRCLE = 2.0;
const float SHADER_STROKED_CIRCLE = 3.0; const float SHADER_STROKED_CIRCLE = 3.0;
// Minimum line width
const float MIN_WIDTH = 1.0;
attribute vec4 attrShaderParams; attribute vec4 attrShaderParams;
varying vec4 shaderParams; varying vec4 shaderParams;
varying vec2 circleCoords;
void main() void main()
{ {
@ -45,8 +49,8 @@ void main()
float worldScale = gl_ModelViewMatrix[0][0]; float worldScale = gl_ModelViewMatrix[0][0];
float scale; float scale;
// Make lines appear to be at least 1 pixel width // Make lines appear to be at least 1 pixel wide
if( worldScale * lineWidth < 1.0 ) if( worldScale * lineWidth < MIN_WIDTH )
scale = 1.0 / ( worldScale * lineWidth ); scale = 1.0 / ( worldScale * lineWidth );
else else
scale = 1.0; scale = 1.0;
@ -54,6 +58,37 @@ void main()
gl_Position = gl_ModelViewProjectionMatrix * gl_Position = gl_ModelViewProjectionMatrix *
( gl_Vertex + vec4( shaderParams.yz * scale, 0.0, 0.0 ) ); ( gl_Vertex + vec4( shaderParams.yz * scale, 0.0, 0.0 ) );
} }
else if( ( shaderParams[0] == SHADER_STROKED_CIRCLE ) ||
( shaderParams[0] == SHADER_FILLED_CIRCLE ) )
{
// Compute relative circle coordinates basing on indices
// Circle
if( shaderParams[1] == 1.0f )
circleCoords = vec2( -sqrt( 3.0f ), -1.0f );
else if( shaderParams[1] == 2.0f )
circleCoords = vec2( sqrt( 3.0f ), -1.0f );
else if( shaderParams[1] == 3.0f )
circleCoords = vec2( 0.0f, 2.0f );
// Semicircle
else if( shaderParams[1] == 4.0f )
circleCoords = vec2( -3.0f / sqrt( 3.0f ), 0.0f );
else if( shaderParams[1] == 5.0f )
circleCoords = vec2( 3.0f / sqrt( 3.0f ), 0.0f );
else if( shaderParams[1] == 6.0f )
circleCoords = vec2( 0.0f, 2.0f );
// Make the line appear to be at least 1 pixel wide
float lineWidth = shaderParams[3];
float worldScale = gl_ModelViewMatrix[0][0];
float scale;
// Make lines appear to be at least 1 pixel width
if( worldScale * lineWidth < MIN_WIDTH )
shaderParams[3] = shaderParams[3] / ( worldScale * lineWidth );
gl_Position = ftransform();
}
else else
{ {
// Pass through the coordinates like in the fixed pipeline // Pass through the coordinates like in the fixed pipeline