Then we need to tell OpenGL how to unpack our RGBA bytes. Create a new OpenGL texture int textureId = glGenTextures() Each operation related to that texture will use that identifier so we need to bind it. First of all we need to create a new texture identifier. The next step is to upload the texture into the graphics card memory. Some drivers remove that constraint but it’s better to stick to it to avoid problems. One important thing to remember is that OpenGL, for historical reasons, requires that texture images have a size (number of texels in each dimension) of a power of two (2, 4, 8, 16. format: The target format into which the image should be decoded (RGBA).īyteBuffer buf = ByteBuffer.allocateDirect(Ĥ * decoder.getWidth() * decoder.getHeight()) ĭcode(buf, decoder.getWidth() * 4, Format.RGBA).In this case it will be the number of bytes per line. stride: Specifies the distance in bytes from the start of a line to the start of the next line.buffer: The ByteBuffer that will hold the decoded image (since each pixel uses four bytes its size will be 4 width height).The decode method requires three parameters: The PNG image will be decoded in RGBA format (RGB for Red, Green, Blue and A for Alpha or transparency) which uses four bytes per pixel. Then we need to decode the PNG image and store its content into a buffer by using the decode method of the PNGDecoder class. Our texture image will be located in the resources folder and can be accessed as a CLASSPATH resource and passed as an input stream to the PNGDecoder class. Now we will create a new Texture class that will perform all the necessary steps to load a texture. Since we are using GLSL shaders it is not required anymore. This is true if you are using the fixed-function pipepline. One thing that you may see in some web pages is that the first thing we must do is enable the textures in our OpenGL context by calling glEnable(GL_TEXTURE_2D). So the associated coordinates array will be like this: float positions = new float Īnd define the version of the library to use.

In order to draw a cube we just need to define eight vertices. With the code base we have created, in order to draw a cube we just need to correctly define the coordinates of a cube and it should be drawn correctly. In order to show all the concepts related to textures we will transform the quad that we have been using in previous chapters into a 3D cube. In this chapter we will learn how to load textures and use them in the rendering process.

Java lwjgl 3 drawing a 3d cube