I have these lines of code in my custom TileEntityRenderer:

public void render(MyTileEntity tile, float partialTicks, MatrixStack matrix, IRenderTypeBuffer buffer, int light, int overlay) {
    ItemStack stack = tile.getWantingItem();
    if (!stack.isEmpty()) {
        matrix.pushPose();
        matrix.translate(0.5D, 1.6D, 0.5D);
        matrix.scale(0.9f, 0.9f, 0.9f);
        matrix.mulPose(Vector3f.YP.rotationDegrees(degrees++ / 2));
        renderItem(stack, matrix, buffer, light);
        matrix.popPose();
    }
}

private void renderItem(ItemStack stack, MatrixStack matrix, IRenderTypeBuffer bufferIn, int combinedLightIn) {
    Minecraft.getInstance().getItemRenderer().renderStatic(stack, ItemCameraTransforms.TransformType.FIXED, combinedLightIn,
            OverlayTexture.NO_OVERLAY, matrix, bufferIn);
}

The `tile.getWantingItem()` creates an ItemStack from Item.

The code above renders the item on top of the block, rotating, but very dark.

However, I also have another TileEntityRenderer that renders item correctly, with lights, and the same code except the `tile.getWantingItem()` part. It instead gets ItemStack from its inventory.

I think the problem might be the creation of ItemStack, but I don't really know. Can anyone tell me how to fix this?

I am not using mojang mappings, but i think you need to use the combinedLight and combinedOverlay for rendering.

Like this:

renderer.renderItem(stack, ItemCameraTransforms.TransformType.FIXED, combinedLightIn, combinedOverlayIn, matrixStackIn, bufferIn);