Some very simple tesselation example 
You can modify the inner / outer factors using the sliders (top = inner, bottom = outer). Currently int division is enabled (equal_spacing). You can enable float division with fractional_even_spacing or fractional_odd_spacing.
Untesselated:
Tesselated with inner = 20 and outer = 20:
shader.glsl:
#ifdef _VERTEX_
// Vertex shader, simply pass world position to
// the tesselation control shader
in vec4 p3d_Vertex;
out vec3 controlpoint_wor;
void main() {
controlpoint_wor = p3d_Vertex.xyz;
}
#endif
#ifdef _TESSCONTROL_
// Compute the tesselation factors here
layout(vertices = 3) out;
in vec3 controlpoint_wor[];
out vec3 tcPosition[];
uniform float TessLevelInner = 4.0;
uniform float TessLevelOuter = 4.0;
#define ID gl_InvocationID
void main()
{
tcPosition[ID] = controlpoint_wor[ID];
if (ID == 0) {
gl_TessLevelInner[0] = TessLevelInner;
gl_TessLevelOuter[0] = TessLevelOuter;
gl_TessLevelOuter[1] = TessLevelOuter;
gl_TessLevelOuter[2] = TessLevelOuter;
}
}
#endif
#ifdef _TESSEVAL_
// This shader creates the triangles
layout(triangles, equal_spacing, ccw) in;
in vec3 tcPosition[];
out vec3 tePosition;
out vec3 tePatchDistance;
uniform mat4 p3d_ModelViewProjectionMatrix;
void main()
{
vec3 p0 = gl_TessCoord.x * tcPosition[0];
vec3 p1 = gl_TessCoord.y * tcPosition[1];
vec3 p2 = gl_TessCoord.z * tcPosition[2];
tePatchDistance = gl_TessCoord;
tePosition = (p0 + p1 + p2);
gl_Position = p3d_ModelViewProjectionMatrix * vec4(tePosition, 1);
}
#endif
#ifdef _FRAGMENT_
// Final rendering (I know gl_FragColor is deprecated)
void main() {
gl_FragColor = vec4(1,0,0,1);
}
#endifmain.py:
from direct.showbase.ShowBase import ShowBase
from ShaderCombiner import ShaderCombiner
from direct.gui.DirectSlider import DirectSlider
from panda3d.core import GeomPatches, GeomVertexFormat, GeomVertexWriter, GeomVertexData, Geom, GeomNode
class MyApp(ShowBase):
def __init__(self):
ShowBase.__init__(self)
# Camera stuff
base.disableMouse()
base.camera.setPos(0, -3, 0)
base.camera.lookAt(0, 0, 0)
# Toggle wireframe so we can see the vertices
base.toggleWireframe()
# For reloading the shaders
self.accept("r", self.loadShader)
# Create the patch
form = GeomVertexFormat.getV3()
vdata = GeomVertexData("vertices", form, Geom.UHStatic)
vertexWriter = GeomVertexWriter(vdata, "vertex")
vertexWriter.addData3f(0, 0, 0)
vertexWriter.addData3f(1, 0, 0)
vertexWriter.addData3f(1, 0, 1)
vertexWriter.addData3f(0, 0, 1)
patches = GeomPatches(3, Geom.UHStatic)
patches.addVertex(0)
patches.addVertex(1)
patches.addVertex(3)
patches.closePrimitive()
patches.addConsecutiveVertices(1, 3)
patches.closePrimitive()
gm = Geom(vdata)
gm.addPrimitive(patches)
gn = GeomNode("model")
gn.addGeom(gm)
self.tesselatedQuad = render.attachNewNode(gn)
self.tesselatedQuad.setPos(-0.5, 0, -0.5)
# Load tesselation shader
self.loadShader()
# Set initial tesselation factors
self.tesselatedQuad.setShaderInput("TessLevelInner", 5.0)
self.tesselatedQuad.setShaderInput("TessLevelOuter", 5.0)
# Sliders to modify the tesselation factors
self.tessInnerSlider = DirectSlider(range=(1, 20), value=8.0, pageSize=1.0, pos=(
0, 0, 0.8), scale=(1.1, 1, 0.4), command=self.setInnerTess)
self.tessOuterSlider = DirectSlider(range=(1, 20), value=8.0, pageSize=1.0, pos=(
0, 0, 0.7), scale=(1.1, 1, 0.4), command=self.setOuterTess)
def setInnerTess(self):
self.tesselatedQuad.setShaderInput(
"TessLevelInner", float(self.tessInnerSlider['value']))
def setOuterTess(self):
self.tesselatedQuad.setShaderInput(
"TessLevelOuter", float(self.tessOuterSlider['value']))
def loadShader(self):
# This simply loads the tesselation shaders
sha = ShaderCombiner.createGlslShader(
["shader.glsl"], False, "shader", glslversion=400, externals=None, defines=None, has_tesselation=True)
self.tesselatedQuad.setShader(sha)
app = MyApp()
app.run()ShaderCombiner.py:
from os.path import join
from panda3d.core import Shader
from os import makedirs
from os.path import isdir
class ShaderCombiner:
__tmp_path = "shader_dump"
@classmethod
def setTempPath(self, p):
self.__tmp_path = p
@classmethod
def ensureTempPath(self):
if isdir(self.__tmp_path):
return
try:
makedirs(self.__tmp_path)
except Exception, msg:
print "Could not create shader dir at", self.__tmp_path, ":", msg
@classmethod
def getShaderFileContents(self, filename):
with open(filename) as f:
return f.read()
@classmethod
def writeShaderFileContents(self, filename, content, append=False):
with open(filename, 'a' if append else 'w') as f:
f.write(content)
@classmethod
def parseShaderContent(self, content):
content = content.replace("\r", "")
return content
@classmethod
def createGlslShader(self, files, has_geometry, name, glslversion=130, externals=None, defines=None, has_tesselation=False):
dbg = "Creating shader '" + str(name) + "' with glslversion " + str(glslversion)
if has_geometry:
dbg += " (geometry)"
if has_tesselation:
dbg += " (tesselated)"
print dbg
self.ensureTempPath()
if type(files) == str:
files = [files]
if type(files) != list:
files = list(files)
files = [] + files
header = "//GLSL\n"
header += "#version " + str(glslversion) + "\n"
if defines is not None:
for dname, dvalue in defines.items():
header += "#define " + dname + " " + str(dvalue) + "\n"
content_vshader = header
content_fshader = header
content_gshader = header
content_tessControl = header
content_tessEval = header
content_vshader += "#define _VERTEX_\n\n#define VARIABLE out\n\n"
if has_geometry:
content_fshader += "#extension GL_ARB_fragment_layer_viewport : enable\n"
content_fshader += "#define _FRAGMENT_\n\n#define VARIABLE in\n\n"
if has_geometry:
content_gshader += "#extension GL_EXT_geometry_shader4 : enable\n"
content_gshader += "#extension GL_ARB_fragment_layer_viewport : enable\n"
content_gshader += "#define _GEOMETRY_\n\n"
if has_tesselation:
content_tessControl += "#define _TESSCONTROL_\n"
content_tessEval += "#define _TESSEVAL_\n"
combined_content = ""
for f in files:
c = self.getShaderFileContents(f)
combined_content += self.parseShaderContent(c) + "\n\n"
if externals is not None:
for eid, source in externals.items():
repl = '#EXTERNAL("' + eid + '")'
content = self.getShaderFileContents(source)
combined_content = combined_content.replace(repl, content)
content_vshader += combined_content
content_fshader += combined_content
content_gshader += combined_content
content_tessControl += combined_content
content_tessEval += combined_content
f_vertex = join(self.__tmp_path, name + "_vertex.glsl")
f_fragment = join(self.__tmp_path, name + "_fragment.glsl")
f_geometry = join(self.__tmp_path, name + "_geometry.glsl")
f_tessControl = join(self.__tmp_path, name + "_tesselationControl.glsl")
f_tessEval = join(self.__tmp_path, name + "_tesselationEvaluation.glsl")
self.writeShaderFileContents(f_vertex, content_vshader)
self.writeShaderFileContents(f_fragment, content_fshader)
if has_geometry:
self.writeShaderFileContents(f_geometry, content_gshader)
if has_tesselation:
self.writeShaderFileContents(f_tessControl, content_tessControl)
self.writeShaderFileContents(f_tessEval, content_tessEval)
args = [f_vertex, f_fragment]
if has_geometry:
args.append(f_geometry)
if has_tesselation:
if not has_geometry:
args.append("")
args.append(f_tessControl)
args.append(f_tessEval)
shader = Shader.load(Shader.SLGLSL, *args)
return shader
