Rotation of one texture stage seems to go all askew

rotate_ts.py

"""
Goal: rotate mask so it stays centered on the X.
What happens: it rotates and shifts, as if the origin of the coordinate system is 
not at the center of the window.
"""
import numpy as np 
from direct.showbase.ShowBase import ShowBase
from panda3d.core import Texture, CardMaker, TextureStage
from direct.gui.OnscreenText import OnscreenText   #for binocular stim
import matplotlib.pyplot as plt
    
class CombineStages(ShowBase):
    """Trying to draw a mask stage over a stim stage and combine them (modulate)"""
    def __init__(self, texture_array):
        super().__init__()

        texture_size = 1024
        self.texture_array = texture_array
        self.mask_angle = 10
        self.mask_position = (0,0)

        #CREATE MASK (zeros on left, 255s on right)
        self.right_mask = 255*np.ones((texture_size,texture_size), dtype=np.uint8)  #should set to 0/1 not 255
        self.right_mask[:, texture_size//2: ] = 0   
        #plt.imshow(self.right_mask, cmap = 'gray')
        #plt.show()

        #CREATE TEXTURE STAGES
        #Grating texture 
        self.grating_texture = Texture("Grating")  #T_unsigned_byte
        self.grating_texture.setup2dTexture(texture_size, texture_size, 
                                            Texture.T_unsigned_byte, Texture.F_luminance) 
        self.grating_texture.setRamImage(self.texture_array)   
        self.left_texture_stage = TextureStage('grating')
        #Mask
        self.right_mask_texture = Texture("right_mask")
        self.right_mask_texture.setup2dTexture(texture_size, texture_size, 
                                               Texture.T_unsigned_byte, Texture.F_luminance) 
        self.right_mask_texture.setRamImage(self.right_mask)  
        self.right_mask_stage = TextureStage('right_mask')
        #Multiply the texture stages together
        self.right_mask_stage.setCombineRgb(TextureStage.CMModulate, 
                                    TextureStage.CSTexture, 
                                    TextureStage.COSrcColor,
                                    TextureStage.CSPrevious, 
                                    TextureStage.COSrcColor)                         
        #CREATE SCENE GRAPH
        cm = CardMaker('card')
        cm.setFrameFullscreenQuad()
        self.left_card = self.aspect2d.attachNewNode(cm.generate())
        #self.left_card.setScale(np.sqrt(8))  #to handle rotations and shifts  
        #Set up grating texture stage and rotate it
        self.left_card.setTexture(self.left_texture_stage, self.grating_texture)  

        #Set up mask texture stage, rotate it and reposition it
        self.left_card.setTexture(self.right_mask_stage, self.right_mask_texture)
        self.left_card.setTexRotate(self.right_mask_stage, self.mask_angle)
        
        #To show where I want the mask centered
        self.title = OnscreenText("x", style = 1, fg = (1,1,1,1), bg = (0,0,0,1),
                                  pos = (0, 0), scale = 0.1)
        
#%%
if __name__ == '__main__':
    texture = np.array(np.random.rand(1024, 1024) * 255, dtype=np.uint8)  
    binocular_drifting = CombineStages(texture)
    binocular_drifting.run()