Draw two cubes using Kivy with different shaders.



multi-mesh.png

Figure 1: Multiple cube meshes

Multiple mesh source code

Expanding on the last example this code demonstrates loading multiple models and using different shaders per model.

import kivy
kivy.require('1.0.7')

from kivy.app import App
from opengl_widget import OpenglWidget


class DemoApp(App):
    pass

if __name__ == '__main__':
    DemoApp().run()
#:kivy 1.0
FloatLayout:
    OpenglWidget:

First shader to create a green object.

"kivy-green.glsl"body

Second shader creates a blue object.

---VERTEX SHADER-------------------------------------------------------
#ifdef GL_ES
    precision highp float;
#endif

attribute vec3  v_pos;
attribute vec4  v_color;

uniform mat4 modelview_mat;
uniform mat4 projection_mat;

varying vec4 frag_color;

void main (void) {
    vec4 pos = modelview_mat * vec4(v_pos,1.0);
    gl_Position = projection_mat * pos;
    frag_color = v_color;
}


---FRAGMENT SHADER-----------------------------------------------------
#ifdef GL_ES
    precision highp float;
#endif

varying vec4 frag_color;
varying vec2 uv_vec;

uniform sampler2D tex;

void main (void){
    gl_FragColor = vec4(0, 0, 1, 1);
}
import os
import sys
from kivy.app import App
from kivy.clock import Clock
from kivy.core.window import Window
from kivy.core.image import Image
from kivy.uix.widget import Widget
from kivy.resources import resource_find
from kivy.graphics.transformation import Matrix
from kivy.graphics.opengl import *
from kivy.graphics import *

from kivy.uix.widget import Widget
from kivy.graphics import Color, Ellipse

from numpy import array


#store a single vertex in this class
class point:
    def __init__(self, p, c=(1, 0, 0, 1)):
	self.x, self.y, self.z = p
	self.vertex = array([self.x, self.y, self.z, c[0], c[1], c[2], c[3]], 'f')


#simple class to create the vertices for a cube for testing.
class cube:
    def __init__(self, p1, color=(1, 0, 0, 1), size=0.5):
	self.color = array([1, 0, 0, 1], 'f')
	self.points = (
	    point((p1[0] - size, p1[1] + size, p1[2] - size), (color)),
	    point((p1[0] - size, p1[1] + size, p1[2] + size), (color)), 
	    point((p1[0] + size, p1[1] + size, p1[2] + size), (color)),
	    point((p1[0] + size, p1[1] + size, p1[2] - size), (color)),

	    point((p1[0] - size, p1[1] - size, p1[2] - size), (color)),
	    point((p1[0] - size, p1[1] - size, p1[2] + size), (color)), 
	    point((p1[0] + size, p1[1] - size, p1[2] + size), (color)),
	    point((p1[0] + size, p1[1] - size, p1[2] - size), (color)),

	    )

    def get_data(self):
	return (
	    self.points[0].vertex, self.points[2].vertex, self.points[1].vertex, 
	    self.points[0].vertex, self.points[3].vertex, self.points[2].vertex, 

	    self.points[0].vertex, self.points[1].vertex, self.points[5].vertex, 
	    self.points[0].vertex, self.points[5].vertex, self.points[4].vertex,

	    self.points[0].vertex, self.points[7].vertex, self.points[3].vertex, 
	    self.points[0].vertex, self.points[4].vertex, self.points[7].vertex,

	    self.points[6].vertex, self.points[2].vertex, self.points[3].vertex, 
	    self.points[6].vertex, self.points[3].vertex, self.points[7].vertex, 

	    self.points[6].vertex, self.points[1].vertex, self.points[2].vertex,
	    self.points[6].vertex, self.points[5].vertex, self.points[1].vertex,

	    self.points[6].vertex, self.points[4].vertex, self.points[5].vertex,
	    self.points[6].vertex, self.points[7].vertex, self.points[4].vertex,
	)


#custom widget for render our scene into
class OpenglWidget(Widget):

    def __init__(self, **kwargs):
	self.instructions = InstructionGroup()
	self.canvas = RenderContext(compute_normal_mat=True)
	self.canvas.shader.source = resource_find('kivy.glsl')

	#create first shader for cube 1
	self.cube1 = RenderContext(compute_normal_mat=True)
	self.cube1.shader.source = resource_find('kivy-blue.glsl')

	#create first shader for cube 2
	self.cube2 = RenderContext(compute_normal_mat=True)
	self.cube2.shader.source = resource_find('kivy-green.glsl')

	#create 2 cubes for testing
	cube1 = cube((0, -4, 0), size = 2.0)
	cube2 = cube((0, 4, 0), size = 2.0)

	#generate vertex array for cube 1
	self.vertices_cube1 = []
	for item in cube1.get_data():
	    for a in item:
		self.vertices_cube1.append(a)

	#generate vertex array for cube 2
	self.vertices_cube2 = []
	for item in cube2.get_data():
	    for a in item:
		self.vertices_cube2.append(a)

	#calcualte indices for both cubes
	self.indices_cube1 = range(0, 36)
	self.indices_cube2 = range(0, 36)

	#add our render contexts to an instruction group for drawing
	self.instructions.add(self.cube1)
	self.instructions.add(self.cube2)
	self.canvas.add(self.instructions)
	with self.canvas:
	    self.cb = Callback(self.setup_gl_context)
	    PushMatrix()
	    self.scene()
	    PopMatrix()
	    self.cb = Callback(self.reset_gl_context)
	Clock.schedule_interval(self.update_glsl, 1 / 60.)

    #create our scene and update our two models
    def scene(self):
	Color(0, 0, 0, 1)
	with self.cube2:
	    self.cube1_mesh()
	with self.cube1:
	    self.cube2_mesh()

    def setup_gl_context(self, *args):
	glEnable(GL_DEPTH_TEST)

    def reset_gl_context(self, *args):
	glDisable(GL_DEPTH_TEST)

    #setup the projection matrices 
    def update_glsl(self, *largs):
	aspect = float(self.width) / float(self.height)
	projection_mat = Matrix()
	projection_mat.perspective(45.0, aspect, 1.0, 80.0)
	model = Matrix().look_at(
	    0.0, 0.0, 25.0,
	    0.0, 0.0, 0.0,
	    0.0, 1.0, 0.0)

	self.canvas['projection_mat'] = projection_mat
	self.canvas['modelview_mat'] = model

	self.cube1['projection_mat'] = projection_mat
	self.cube1['modelview_mat'] = model

	self.cube2['projection_mat'] = projection_mat
	self.cube2['modelview_mat'] = model
	self.rot_cube1.angle += 1
	self.rot_cube2.angle += 1

    def cube1_mesh(self):
	Color(0, 0, 0, 1)
	PushMatrix()

	self.rot_cube1 = Rotate(1, 0, 1, 0)

	vertex_format = [
	    ('v_pos', 3, 'float'),
	    ('v_color', 4, 'float'),
	]

	UpdateNormalMatrix()
	self.mesh1 = Mesh(
	    vertices=self.vertices_cube1,
	    indices=self.indices_cube1,
	    fmt=vertex_format,
	    mode='triangles',
	)

	PopMatrix()

    def cube2_mesh(self):

	PushMatrix()
	Color(0, 0, 0, 1)
	self.rot_cube2 = Rotate(1, 0, -1, 0)

	vertex_format = [
	    ('v_pos', 3, 'float'),
	    ('v_color', 4, 'float'),
	]

	UpdateNormalMatrix()
	self.mesh2 = Mesh(
	    vertices=self.vertices_cube2,
	    indices=self.indices_cube2,
	    fmt=vertex_format,
	    mode='triangles',
	)
	PopMatrix()

    def setup_scene(self):
	Color(0, 0, 0, 1)
	self.cube1_mesh()
	self.cube1_mesh()

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