Overlay one 2D image onto another? PyOpenGL?

Question

I am currently using PyOpenGL with PyGame to write code for a top-down 2D side scroller.

The code shown below will generate a 2D image in a window.

The image that is added is the background. I would now like to add sprites to the background using OpenGL. In other words, I want to overlay one 2D image on top of another. I cannot seem to find a good way to do this.

import pygame
from pygame.locals import *
from OpenGL.GL import *
from OpenGL.GLU import *
from screenDictionary import *

### Initialize variables ###
gameOn = True
dispWidth = 1920
dispHeight = 1024
bgImg = 'A1_64.png'
bgImg2 = 'HookedFront64.png'
transTuple = (255, 0, 255)
blackTuple = (100, 100, 100)
screenX = 0
screenY = 0

### Initialize display ###
def createDisplay(dispWidth, dispHeight):
    pygame.init()
    screen = pygame.display.set_mode((dispWidth, dispHeight), DOUBLEBUF|OPENGL)
    pygame.display.set_caption('Hooked')
    return screen

def createSurfaces(screen):
    background = pygame.Surface(screen.get_size())
    background.fill(blackTuple)
    sprite = pygame.Surface(screen.get_size())
    sprite.set_colorkey(transTuple)
    return background

def loadScene(bgImg):
    img = pygame.image.load(bgImg)
    textureData = pygame.image.tostring(img, "RGB", 1)
    width = img.get_width()
    height = img.get_height()
    bgImgGL = glGenTextures(1)
    glBindTexture(GL_TEXTURE_2D, bgImgGL)
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR)
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, width, height, 0, GL_RGB, GL_UNSIGNED_BYTE, textureData)
    glEnable(GL_TEXTURE_2D)

def placeScene():
    glLoadIdentity()
    gluPerspective(90, 1, 0.05, 100)
    glTranslatef(0,0,0)
    glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT)
    glBegin(GL_QUADS)
    glTexCoord2f(0,0)
    glVertex3f(-4,-4,-4)
    glTexCoord2f(0,1)
    glVertex3f(-4,4,-4)
    glTexCoord2f(1,1)
    glVertex3f(4,4,-4)
    glTexCoord2f(1,0)
    glVertex3f(4,-4,-4)
    glEnd()    

screen = createDisplay(dispWidth, dispHeight)  
background = createSurfaces(screen)
mapParams = screenDictionary(screenX, screenY)
bgImg = mapParams[0]
loadScene(bgImg)
loadScene(bgImg2)
loadScene(bgImg)

###Run the game###
while gameOn:
    placeScene()
    pygame.display.flip()
    pygame.time.wait(1)
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            pygame.quit()
            gameOn = False

Welcome to SO. Please read this [how-to-ask](http://stackoverflow.com/help/how-to-ask) and follow the guidelines there to refine your question with additional information, such as code and error message to describe your programming problem. — thewaywewere, May 23 '17 at 16:07
Why are you using GL ? I also did that, but only for 3D. But I assume you want 2D, so you can use glVertex2f and the order counts. — Luatic, May 23 '17 at 18:50
I chose GL for hardware acceleration capabilities. Would you recommend an alternative to OpenGL? — Matthew Tharp, May 23 '17 at 20:49

score 0 · Answer 1 · answered May 23 '17 at 21:01

Problem solved.

Changes made: used gluOrtho2D instead of gluPerspective. Used glVertex2f instead of glVertex3f.

Most important change: Removed glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT) This was clearing the scene every time it was executed... DUH! Still learning openGL, but will leave this here in case anyone else is dumb like me and runs into a similar problem.

Overlay one 2D image onto another? PyOpenGL?

1 Answers1