OpenGL 3D Game Tutorial 27: Skybox

instead of changing the view matrix in the renderer you can treat the position of the vertex as a vector by replacing vec4(position, 1.0) with vec4(position, 0.0) when you calculate gl_Position

i love your videos, but i have a problem and is that when rendering the sky box, this does not look right when being reflected by water

For people who experience serious problems like flickering in the edges (seams) of the skybox just add this line somewhere in your project (it need to be called just one): glEnable(GL_TEXTURE_CUBE_MAP_SEAMLESS)

Hi! It all looks wonderful, but I would like to see the sky (the top of the cube) without the ferns, player and other stuff… How can I do that?
P.S.: I hope I'm not too buggy with my questions! 😀

One quick tip I have for skyboxes: this skybox will clip through the terrain and reduce the draw distance, wasting render time on objects/terrain which is beyond the bounds of the skybox. You can fix this by adding this code to the start of the skybox render method:

glDepthMask(GL_FALSE);
glDepthRange(1f, 1f);

And adding this code to the end of the method:

glDepthRange(0f, 1f);
glDepthMask(GL_TRUE);

This for one stops the skybox from being drawn onto the depth buffer, and two makes the skybox draw behind everything else, which keeps everything in view and puts the skybox at the back of the scene, so it doesn't cut any objects off.

I didn't notice it before but when I looked at the corners of the skybox I saw that the corners were a little bit glitchy. How can this be fixed?

I don't know if someone else has mentioned this already, but in the vertex shader it's also possible to multiply the view matrix with vec4(position, 0.0f) instead of vec4(position, 1.0f). Because of the 0.0f the view matrix' translation won't affect the vector at all, but the rotation (and scale) will. That way you don't have to create a modified view matrix just for this shader.
After that multiplication the vector's w coordinate does need to be manually set back to 1.0f though, otherwise the projection matrix won't apply correctly anymore:

vec4 untranslated_view = viewMatrix * vec4(position, 0.0f);
untranslated_view.w = 1.0f;
gl_Position = projectionMatrix * untranslated_view;

It probably doesn't make any difference for the performance, but it's still nice, I suppose. ^w^

All the textures load fine, but the "top.png" is all multi colored lines, like an old TV(the static looking stuff). why is this? why just top.png and no others ? I would appreciate help from anyone

If you render the skybox first with depth testing disabled, the skybox wont collide with the terrain like at 18:50.

Is it just my terrain that won't render at coordinates like 1, 1 and -2, -2?

If anybody is getting this error: Exception in thread "main" java.lang.IllegalArgumentException: ByteBuffer is not direct
In the loader class, in the decodeTextureFile method, look for where you allocate the bytebuffer and change that line to: buffer = ByteBuffer.allocateDirect(4 * width * height);

My skybox was black,I accidentally forgot to multiple width by 4 at pngdecoder..now its working…good tutorial Tnx Matrix.

I am having trouble with the downloaded code in the loader class.
Format.RGBA
none of the imports I can use appear to work for that.

why dont u just call import static org.lwjgl.opengl.GL13.*;
or does it effect on memory?

why not skydome?

Hey, I just wanted to say thanks with this for teaching me so much:
i.imgur dot com/tInCooh.png
<3

In the Loader method I keep getting a problem with the Format.RGBA constant. >.< it can find one but it expects another.

Sorry to bother you with this 2 years after upload but i cant get that Skybox working … it's just not rendering to the screen :/ And I can't find the error I made even after looking your vid about 5 times D: Do you coincidentally have the code for this episode so I can copy it ? ^^'

Thanks for these tutorials. I'd rather build my own engine than use someone else's. I just want to understand all the details, and i feel that using some other already complete engine won't get me there.

I spent a good couple of hours tracking down my issue of the Skybox not being drawn. Eventually I figured out that the first thing I needed to do in the SkyboxRenderer class's Render method was disable backface culling. Then the last thing before leaving the method was re-enable backface culling.

There is a problem with the skybox code in dropbox. When I them it says "We can't find the page your looking for". Could someone please put the code in the comments?

Sky skybox isnt a box and is textures completly wrong: http://imgur.com/a/Ct9PC

Here my code:
public int loadCubeMap(String[] textureFiles) {
int texID = GL11.glGenTextures();
GL13.glActiveTexture(GL13.GL_TEXTURE0);
GL11.glBindTexture(GL13.GL_TEXTURE_CUBE_MAP, texID);

for(int i = 0; i < textureFiles.length; i++) {
TextureData data = decodeTextureFile("res/skybox/cloud/" + textureFiles[i] + ".png");
GL11.glTexImage2D(GL13.GL_TEXTURE_CUBE_MAP_POSITIVE_X + i, 0, GL11.GL_RGBA, data.getWidth(), data.getHeight(), 0, GL11.GL_RGBA, GL11.GL_UNSIGNED_BYTE, data.getBuffer());
}
GL11.glTexParameteri(GL13.GL_TEXTURE_CUBE_MAP, GL11.GL_TEXTURE_MAG_FILTER, GL11.GL_LINEAR);
GL11.glTexParameteri(GL13.GL_TEXTURE_CUBE_MAP, GL11.GL_TEXTURE_MIN_FILTER, GL11.GL_LINEAR);
GL11.glTexParameteri(GL13.GL_TEXTURE_CUBE_MAP, GL11.GL_TEXTURE_WRAP_S, GL12.GL_CLAMP_TO_EDGE);
GL11.glTexParameteri(GL13.GL_TEXTURE_CUBE_MAP, GL11.GL_TEXTURE_WRAP_T, GL12.GL_CLAMP_TO_EDGE);
textures.add(texID);
return texID;
}

SkyBoxRenderer:
private static String[] TEXTURE_FILES = { "right", "left", "top", "bottom", "back", "front" };
private RawModel cube;
private int texture;
private SkyboxShader shader;

public SkyboxRenderer(Loader loader, Matrix4f projectionMatrix) {
cube = loader.loadToVAO(VERTICES, 3);
texture = loader.loadCubeMap(TEXTURE_FILES);
shader = new SkyboxShader();
shader.start();
shader.loadProjectionMatrix(projectionMatrix);
shader.stop();
}

public void render(Camera camera) {
shader.start();
shader.loadViewMatrix(camera);
GL30.glBindVertexArray(cube.getVaoID());
GL20.glEnableVertexAttribArray(0);
GL13.glActiveTexture(GL13.GL_TEXTURE0);
GL11.glBindTexture(GL13.GL_TEXTURE_CUBE_MAP, texture);
GL11.glDrawArrays(GL11.GL_TRIANGLES, 0, cube.getVertexCount());
GL20.glDisableVertexAttribArray(0);
GL30.glBindVertexArray(0);
shader.stop();
}

I find it mildly amusing that the skybox coordinates take up a kilobyte