Re: [osg-users] ClipNode Opposite Behavior
whatever float your boat... ;)
Here's a shader routine that evaluates if a fragment coordinate in object
space is within a polygon described by up to 16 vertices in the x/y plane.
We use it to cut a hole into a city scenario, so we can see into the
basement of a house. The shader does a simple point in polygon test.
The weird osgShadow_ naming for my uniforms comes from the fact that
we've extended the one of OSG's shadow implementations of OSG with support
for cutting holes into the shadowed scene.
const char MyShadowMap::fragmentShaderSource_HoleCutter[] =
{
#version 120\n
uniform vec2 osgShadow_polygon[16]; \n
uniform float osgShadow_nvert; \n
\n
bool pnpoly(vec2 test)\n
{\n
bool c = false;
if (osgShadow_nvert = 3)\n
{\n
int i, j;\n
for (i = 0, j = int(osgShadow_nvert) - 1; i
int(osgShadow_nvert); j = i++) {\n
if (((osgShadow_polygon[i].ytest.y) !=
(osgShadow_polygon[j].ytest.y)) \n
(test.x (osgShadow_polygon[j].x -
osgShadow_polygon[i].x) * (test.y - osgShadow_polygon[i].y) /
(osgShadow_polygon[j].y - osgShadow_polygon[i].y) +
osgShadow_polygon[i].x))\n
c = !c;\n
}\n
}\n
return c;\n
}\n
\n
bool is_hole(vec3 pos)\n
{\n
return pnpoly(pos.xy);\n
}\n
};
static const char fragmentShaderSource[] =
#version 120\n
\n
bool is_hole(vec3 pos);\n
\n
void main(void) \n
{ \n
\n
// early discard
// NOTE: we've previously set up gl_TexCoord[4].xyz to contain vertex
coordinates
// so we don't require a vertex shader here that passes us a varying
of vertex coords.
if (is_hole(gl_TexCoord[4].xyz)) discard;\n
\n
// remainder of shader is here
}\n;
2015-08-17 3:03 GMT+02:00 Erik Hensens ehens...@hunter.com:
I just wanted to mention that I never got the fragment shader approach to
work for what I wanted. I ended up using polygon tessellation to build the
geometry out of triangles.
Thanks anyway to everyone who attempted to help!
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Re: [osg-users] ClipNode Opposite Behavior
I just wanted to mention that I never got the fragment shader approach to work for what I wanted. I ended up using polygon tessellation to build the geometry out of triangles. Thanks anyway to everyone who attempted to help! -- Read this topic online here: http://forum.openscenegraph.org/viewtopic.php?p=64791#64791 ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
Re: [osg-users] ClipNode Opposite Behavior
If you want the hole to be specified in object local coordinates, use
gl_Vertex.
Getting world coordinates is a bit more tricky, you would need to have the
transformation matrix between object coordinates and world coordinates
accessible
in the vertex (or fragment) shader.
Definitely do not use gl_FragCoord - because this one is in 2D screen space.
Christian
2015-07-26 15:46 GMT+02:00 Glenn Waldron gwald...@gmail.com:
Erick,
gl_FragCoord is almost certainly not what you want (Google it). Try
something like this:
Vertex shader:
uniform vec3 center;
varying float dist;
void main()
{
vec4 vertex = gl_ModelViewMatrix * gl_Vertex;
dist = length(center - vertex.xyz);
}
Fragment shader:
uniform float rad;
varying float dist;
void main()
{
if ( rad dist )
discard;
else
gl_FragColor = ...;
}
Glenn Waldron / @glennwaldron
On Fri, Jul 24, 2015 at 9:22 AM, Erik Hensens ehens...@hunter.com wrote:
Thanks Christian. It's funny you mention that because since I'm not
setting the color, the quad looks like an old television tuned to a
frequency not in service, i.e. static or snow. I think every time the
quad is rendered each fragment's color is set to whatever value is in some
uninitialized portion of memory, and each fragment changes color each time
it is rendered. Quite a funny effect!
I added the following line to set the color, and now it is always blue,
but it's still not putting a hole in my quad, it's all there or all gone
depending on whether I say if (fDist rad) or if (fDist rad):
Code:
// The fragment shader program source code
std::string szFragSource(
uniform vec3 center;\n
uniform float rad;\n
void main()\n
{\n
float fDistX = gl_FragCoord.x - center.x;\n
float fDistY = gl_FragCoord.y - center.y;\n
float fDistZ = gl_FragCoord.z - center.z;\n
float fDist = sqrt(fDistX * fDistX + fDistY * fDistY + fDistZ *
fDistZ);\n
gl_FragColor = vec4(0.0,0.0,1.0,1.0);\n
if (fDist rad) discard;\n
}\n
);
Any other ideas about why my code doesn't achieve what I want? For
example, am I using gl_FragCoord correctly? Are there other errors in my
frag source?
Thanks again!
cbuchner1 wrote:
I believe your fragment shader is not setting the output fragment color
at all, which is a minimum requirement for a fragment shader to work.
Christian
2015-07-23 23:59 GMT+02:00 Erik Hensens ():
Sorry for the triplicate post, I received an error message on trying
to post until I removed the quotes...
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Re: [osg-users] ClipNode Opposite Behavior
Erick,
gl_FragCoord is almost certainly not what you want (Google it). Try
something like this:
Vertex shader:
uniform vec3 center;
varying float dist;
void main()
{
vec4 vertex = gl_ModelViewMatrix * gl_Vertex;
dist = length(center - vertex.xyz);
}
Fragment shader:
uniform float rad;
varying float dist;
void main()
{
if ( rad dist )
discard;
else
gl_FragColor = ...;
}
Glenn Waldron / @glennwaldron
On Fri, Jul 24, 2015 at 9:22 AM, Erik Hensens ehens...@hunter.com wrote:
Thanks Christian. It's funny you mention that because since I'm not
setting the color, the quad looks like an old television tuned to a
frequency not in service, i.e. static or snow. I think every time the
quad is rendered each fragment's color is set to whatever value is in some
uninitialized portion of memory, and each fragment changes color each time
it is rendered. Quite a funny effect!
I added the following line to set the color, and now it is always blue,
but it's still not putting a hole in my quad, it's all there or all gone
depending on whether I say if (fDist rad) or if (fDist rad):
Code:
// The fragment shader program source code
std::string szFragSource(
uniform vec3 center;\n
uniform float rad;\n
void main()\n
{\n
float fDistX = gl_FragCoord.x - center.x;\n
float fDistY = gl_FragCoord.y - center.y;\n
float fDistZ = gl_FragCoord.z - center.z;\n
float fDist = sqrt(fDistX * fDistX + fDistY * fDistY + fDistZ *
fDistZ);\n
gl_FragColor = vec4(0.0,0.0,1.0,1.0);\n
if (fDist rad) discard;\n
}\n
);
Any other ideas about why my code doesn't achieve what I want? For
example, am I using gl_FragCoord correctly? Are there other errors in my
frag source?
Thanks again!
cbuchner1 wrote:
I believe your fragment shader is not setting the output fragment color
at all, which is a minimum requirement for a fragment shader to work.
Christian
2015-07-23 23:59 GMT+02:00 Erik Hensens ():
Sorry for the triplicate post, I received an error message on trying
to post until I removed the quotes...
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Re: [osg-users] ClipNode Opposite Behavior
I believe your fragment shader is not setting the output fragment color at all, which is a minimum requirement for a fragment shader to work. Christian 2015-07-23 23:59 GMT+02:00 Erik Hensens ehens...@hunter.com: Sorry for the triplicate post, I received an error message on trying to post until I removed the quotes... -- Read this topic online here: http://forum.openscenegraph.org/viewtopic.php?p=64458#64458 ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
Re: [osg-users] ClipNode Opposite Behavior
Thanks Christian. It's funny you mention that because since I'm not setting the
color, the quad looks like an old television tuned to a frequency not in
service, i.e. static or snow. I think every time the quad is rendered each
fragment's color is set to whatever value is in some uninitialized portion of
memory, and each fragment changes color each time it is rendered. Quite a funny
effect!
I added the following line to set the color, and now it is always blue, but
it's still not putting a hole in my quad, it's all there or all gone depending
on whether I say if (fDist rad) or if (fDist rad):
Code:
// The fragment shader program source code
std::string szFragSource(
uniform vec3 center;\n
uniform float rad;\n
void main()\n
{\n
float fDistX = gl_FragCoord.x - center.x;\n
float fDistY = gl_FragCoord.y - center.y;\n
float fDistZ = gl_FragCoord.z - center.z;\n
float fDist = sqrt(fDistX * fDistX + fDistY * fDistY + fDistZ * fDistZ);\n
gl_FragColor = vec4(0.0,0.0,1.0,1.0);\n
if (fDist rad) discard;\n
}\n
);
Any other ideas about why my code doesn't achieve what I want? For example, am
I using gl_FragCoord correctly? Are there other errors in my frag source?
Thanks again!
cbuchner1 wrote:
I believe your fragment shader is not setting the output fragment color at
all, which is a minimum requirement for a fragment shader to work.
Christian
2015-07-23 23:59 GMT+02:00 Erik Hensens ():
Sorry for the triplicate post, I received an error message on trying to
post until I removed the quotes...
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Re: [osg-users] ClipNode Opposite Behavior
Sorry for the triplicate post, I received an error message on trying to post until I removed the quotes... -- Read this topic online here: http://forum.openscenegraph.org/viewtopic.php?p=64458#64458 ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
Re: [osg-users] ClipNode Opposite Behavior
Thank you both for your input! I'm learning a lot.
I'm new to fragment shaders, so I think that maybe I'm doing something
obviously wrong...
It seems that what I'm doing below should be pretty simple, but it doesn't
work. When I reverse the if (fDist rad) to if (fDist rad) then the entire
thing disappears. Otherwise (the way it is written below), nothing disappears.
Thanks in advance for your help!
Code:
// The group node that contains the test geode
osg::ref_ptrosg::Group pTestGroup = new osg::Group;
// The test geode
osg::ref_ptrosg::Geode pTestGeode = new osg::Geode;
// The geode's geometry
osg::ref_ptrosg::Geometry pTestGeometry = new osg::Geometry;
// The geometry's test vertices
osg::ref_ptrosg::Vec3Array pTestVerticesArray = new osg::Vec3Array;
pTestVerticesArray-push_back(osg::Vec3(0.0f, -2.0f, -2.0f));
pTestVerticesArray-push_back(osg::Vec3(0.0f, -2.0f, 2.0f));
pTestVerticesArray-push_back(osg::Vec3(0.0f, 2.0f, 2.0f));
pTestVerticesArray-push_back(osg::Vec3(0.0f, 2.0f, -2.0f));
// Set this as the vertex array
pTestGeometry-setVertexArray(pTestVerticesArray);
// Define the primitive set
osg::ref_ptrosg::DrawArrays pTestDrawArrays = new
osg::DrawArrays(osg::PrimitiveSet::QUADS, 0,
static_castGLsizei(pTestVerticesArray-size()));
pTestGeometry-addPrimitiveSet(pTestDrawArrays);
// Normalize
osg::ref_ptrosg::StateSet pTestStateSet =
pTestGeometry-getOrCreateStateSet();
pTestStateSet-setMode(GL_NORMALIZE, osg::StateAttribute::ON);
// Add the test geometry to the geode
pTestGeode-addDrawable(pTestGeometry);
// Add the geode to the group
pTestGroup-addChild(pTestGeode);
// The fragment shader program source code
std::string szFragSource(
uniform vec3 center;\n
uniform float rad;\n
void main()\n
{\n
float fDistX = gl_FragCoord.x - center.x;\n
float fDistY = gl_FragCoord.y - center.y;\n
float fDistZ = gl_FragCoord.z - center.z;\n
float fDist = sqrt(fDistX * fDistX + fDistY * fDistY + fDistZ * fDistZ);\n
if (fDist rad) discard;\n
}\n
);
// Create the fragment shader
osg::ref_ptrosg::Shader pFragmentShader = new
osg::Shader(osg::Shader::FRAGMENT, szFragSource.c_str());
// Create the fragment program
osg::ref_ptrosg::Program pProgram = new osg::Program;
// Add the shader to the program
pProgram-addShader(pFragmentShader);
// Get the group node's stateset
osg::StateSet *pStateSet = pTestGroup-getOrCreateStateSet();
// The center of the sphere that I want to define the region that is not drawn
osg::Vec3 tCenter(0.0f, 0.0f, 0.0f);
// The radius of the sphere that I want to define the region that is not drawn
float fRadius = 1.0f;
// Add the center and radius uniforms
osg::ref_ptrosg::Uniform pCenterUniform = new osg::Uniform(center, tCenter);
osg::ref_ptrosg::Uniform pRadiusUniform = new osg::Uniform(rad, fRadius);
pStateSet-addUniform(pCenterUniform);
pStateSet-addUniform(pRadiusUniform);
// Enact this fragment shader on the stateset
pStateSet-setAttributeAndModes(pProgram);
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Re: [osg-users] ClipNode Opposite Behavior
I think you only need to flip the clipping plane around (reverse the plane's normal vector) to get the desired effect. 2015-07-22 21:28 GMT+02:00 Erik Hensens ehens...@hunter.com: Hi everyone! I have a geode that is just a quad rectangular surface and I need to be able to put circular holes in it. To better visualize what I'm talking about, think about a flat slice of Swiss cheese. I just discovered the ClipNode node and I figured I could achieve what I want by adding clip nodes that were the roughly circular, but ClipNode apparently behaves opposite to how I originally thought (I'm new to this). Is there a way to make ClipNode remove parts of the scene instead or keeping only those parts in the clip node region? Or, is there a better way to achieve this flat slice of Swiss cheese shape? Thanks very much in advance! Thank you! Cheers, Erik -- Read this topic online here: http://forum.openscenegraph.org/viewtopic.php?p=64437#64437 ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
Re: [osg-users] ClipNode Opposite Behavior
Are you sure? I think this will leed to nothing being displayed. But I didn't verify it. It is just how I understand clipping. Am 23.07.2015 um 10:35 schrieb Christian Buchner: I think you only need to flip the clipping plane around (reverse the plane's normal vector) to get the desired effect. 2015-07-22 21:28 GMT+02:00 Erik Hensens ehens...@hunter.com mailto:ehens...@hunter.com: Hi everyone! I have a geode that is just a quad rectangular surface and I need to be able to put circular holes in it. To better visualize what I'm talking about, think about a flat slice of Swiss cheese. I just discovered the ClipNode node and I figured I could achieve what I want by adding clip nodes that were the roughly circular, but ClipNode apparently behaves opposite to how I originally thought (I'm new to this). Is there a way to make ClipNode remove parts of the scene instead or keeping only those parts in the clip node region? Or, is there a better way to achieve this flat slice of Swiss cheese shape? Thanks very much in advance! Thank you! Cheers, Erik -- Read this topic online here: http://forum.openscenegraph.org/viewtopic.php?p=64437#64437 ___ osg-users mailing list osg-users@lists.openscenegraph.org mailto:osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org -- *TEXION Software Solutions, Rotter Bruch 26a, D-52068 Aachen* Phone: +49 241 475757-0 Fax: +49 241 475757-29 Web: http://texion.eu eMail: i...@texion.eu ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
Re: [osg-users] ClipNode Opposite Behavior
For creating a circular hole into a plane, clip planes indeed will not work. But generally speaking, flipping a clipping plane reverses its effect (boolean negation) To punch holes in arbitrary geometry at render time, a fragment shader will be a good solution. You can check either object or world coordinates, e.g. distance to a given centerpoint and discard the fragment entirely if the computed distance is below a threshold radius. If you need multiple holes, you need to pass a list of such centerpoints and radii to the shader, e.g. in a Uniform array. Christian 2015-07-23 10:49 GMT+02:00 Werner Modenbach werner.modenb...@texion.eu: Are you sure? I think this will leed to nothing being displayed. But I didn't verify it. It is just how I understand clipping. Am 23.07.2015 um 10:35 schrieb Christian Buchner: I think you only need to flip the clipping plane around (reverse the plane's normal vector) to get the desired effect. 2015-07-22 21:28 GMT+02:00 Erik Hensens ehens...@hunter.com: Hi everyone! I have a geode that is just a quad rectangular surface and I need to be able to put circular holes in it. To better visualize what I'm talking about, think about a flat slice of Swiss cheese. I just discovered the ClipNode node and I figured I could achieve what I want by adding clip nodes that were the roughly circular, but ClipNode apparently behaves opposite to how I originally thought (I'm new to this). Is there a way to make ClipNode remove parts of the scene instead or keeping only those parts in the clip node region? Or, is there a better way to achieve this flat slice of Swiss cheese shape? Thanks very much in advance! Thank you! Cheers, Erik -- Read this topic online here: http://forum.openscenegraph.org/viewtopic.php?p=64437#64437 ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org ___ osg-users mailing listosg-users@lists.openscenegraph.orghttp://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org -- *TEXION Software Solutions, Rotter Bruch 26a, D-52068 Aachen* Phone: +49 241 475757-0 Fax: +49 241 475757-29 Web: http://texion.eu eMail: i...@texion.eu ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
