[vtkusers] How to pass uniform and attribute from host to shader by vtk’s python wrapping.
Ken Martin
ken.martin at kitware.com
Mon Feb 20 08:34:07 EST 2017
If using the new OpenGL rendering backend end see
http://www.vtk.org/Wiki/Shader_In_VTK
On Mon, Feb 20, 2017 at 8:17 AM, Quentan Qi <quentan at gmail.com> wrote:
> Hi,
>
> I want to ask how to pass uniform and attribute from host to shader by
> vtk’s python wrapping.
>
> I follow this instruction to implement this result, but don’t know how to
> pass uniform variables from host to fragment shader.
>
> Could anybody tell me how to do this?
>
> Cheers,
> Quentan
> ------------------------------
>
> - Shader02.py
>
> import vtkimport time
> timer = [time.clock()]resolution = [600, 480]
> file = open('Shader02.vert', 'r')vert = file.read()
> file.close()
> file = open('Shader02.frag', 'r')frag = file.read()
> file.close()
> # Plane. Is there better way to show ShaderToy's effect without use vtkPlaneSource?plane = vtk.vtkPlaneSource()
> plane.SetNormal([0, 0, 1])
> plane.SetResolution(100, 100)
> plane.SetOrigin(-1, -1, 0)
> plane.SetPoint1(1, -1, 1)
> plane.SetPoint2(-1, 1, 0)
> mapper = vtk.vtkPolyDataMapper()
> mapper.SetInputConnection(plane.GetOutputPort())
> actor = vtk.vtkActor()
> actor.SetMapper(mapper)
> actor.GetProperty().SetOpacity(1)
> # Handle the rendering and interactionren = vtk.vtkRenderer()renWin = vtk.vtkRenderWindow()
> renWin.AddRenderer(ren)iren = vtk.vtkRenderWindowInteractor()
> iren.SetRenderWindow(renWin)
> resolutionUniform = vtk.vtkUniformVariables()
> resolutionUniform.SetUniformi('iResolution', 2, resolution)
> timeUniform = vtk.vtkUniformVariables()
> timeUniform.SetUniformf('iGlobalTime', 1, timer)
> # Now let's get down to shader-business...# First we make a ShaderProgram2 and set it up on a date with the RenderWindowpgm = vtk.vtkShaderProgram2()
> pgm.SetContext(renWin)
> # For both the vertex and fragment shader, we need to make a Shader2# Also set them up with the RenderWindow, by asking the ShaderProgram2 for# an introductionshaderv = vtk.vtkShader2()
> shaderv.SetType(vtk.VTK_SHADER_TYPE_VERTEX)
> shaderv.SetSourceCode(vert)
> shaderv.SetContext(pgm.GetContext())
> shaderf = vtk.vtkShader2()
> shaderf.SetType(vtk.VTK_SHADER_TYPE_FRAGMENT)
> shaderf.SetSourceCode(frag)
> shaderf.SetContext(pgm.GetContext())
> shaderf.SetUniformVariables(resolutionUniform) # is this correct?# print shaderf.GetUniformVariables()
> shaderf.SetUniformVariables(timeUniform)# print shaderf.GetUniformVariables()
> # Now we add the shaders to the program
> pgm.GetShaders().AddItem(shaderv)
> pgm.GetShaders().AddItem(shaderf)
> # And tell the actor property that it should totally use this cool programopenGLproperty = actor.GetProperty()
> openGLproperty.SetPropProgram(pgm)
> openGLproperty.ShadingOn()
> # openGLproperty.AddShaderVariable('iGlobalTime', 1, timer) # is this correct?# openGLproperty.AddShaderVariable('iResolution', 2, resolution)
> # Add the actor and set a nice bg color
> ren.AddActor(actor)
> ren.SetBackground(0.3, 0, 0.4)
> ren.SetBackground2(0.1, 0, 0.2)
> ren.SetGradientBackground(1)
> renWin.SetSize(resolution)
>
> iren.Initialize()
> ren.GetActiveCamera().SetPosition(0, -1, 0)
> ren.GetActiveCamera().SetViewUp(0, 0, 1)
> ren.ResetCamera()
> renWin.Render()
> iren.Start()
>
>
> - Shader02.vert
>
> void propFuncVS(void) {
> gl_Position = vec4((gl_Vertex.xy), 0.0, 1.0);
> }
>
>
> - Shader02.frag
>
> // ShaderToy: The Blob// https://www.shadertoy.com/view/XsXGRS
> uniform float iGlobalTime; // not work. uniform or varying?uniform vec2 iResolution;// float iGlobalTime = 1.0;// vec2 iResolution = vec2(600, 480); // This works, but not from host
> #ifdef GL_ESprecision highp float;#endif
> #define AA 4.
> #define CI vec3(.3,.5,.6)#define CO vec3(.2)#define CM vec3(.0)#define CE vec3(.8,.7,.5)
> float metaball(vec2 p, float r)
> {
> return r / dot(p, p);
> }
> vec3 samplef(in vec2 uv)
> {#if 1
> float t0 = sin(iGlobalTime * 1.9) * .46;
> float t1 = sin(iGlobalTime * 2.4) * .49;
> float t2 = cos(iGlobalTime * 1.4) * .57;
>
> float r = metaball(uv + vec2(t0, t2), .33) *
> metaball(uv - vec2(t0, t1), .27) *
> metaball(uv + vec2(t1, t2), .59);
> #else
> float r = length(uv); // test for time-independent
> #endif
> vec3 c = (r > .4 && r < .7)
> ? (vec3(step(.1, r*r*r)) * CE)
> : (r < .9 ? (r < .7 ? CO: CM) : CI);
>
> return c;
> }
> void propFuncFS(void)
> {
> vec2 uv = (gl_FragCoord.xy / iResolution.xy * 2. - 1.)
> * vec2(iResolution.x / iResolution.y, 1) * 1.25;
>
> vec3 col = vec3(0);
> #ifdef AA
> // Antialiasing via supersampling
> float e = 1. / min(iResolution.y , iResolution.x);
> for (float i = -AA; i < AA; ++i) {
> for (float j = -AA; j < AA; ++j) {
> col += samplef(uv + vec2(i, j) * (e/AA)) / (4.*AA*AA);
> }
> }#else
> col += sample(uv);#endif /* AA */
>
> gl_FragColor = vec4(clamp(col, 0., 1.), 1);
> }
>
>
>
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--
Ken Martin PhD
Chairman & CFO
Kitware Inc.
28 Corporate Drive
Clifton Park NY 12065
518 371 3971
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