The renderWarpedTextureOverlay method is being called correctly when inside a 'gas' block, but no overlay is shown.

gistfile1.java

package ljdp.minechem.client;

import java.util.EnumSet;

import org.lwjgl.opengl.GL11;

import ljdp.minechem.common.MinechemBlocks;

import net.minecraft.client.Minecraft;
import net.minecraft.client.renderer.Tessellator;
import net.minecraft.src.FMLRenderAccessLibrary;
import net.minecraftforge.client.MinecraftForgeClient;

import cpw.mods.fml.client.FMLClientHandler;
import cpw.mods.fml.common.ITickHandler;
import cpw.mods.fml.common.TickType;

public class TickHandler implements ITickHandler {

  @Override
	public void tickStart(EnumSet<TickType> type, Object... tickData) {
	}

	@Override
	public void tickEnd(EnumSet<TickType> type, Object... tickData) {
		if(type.contains(TickType.RENDER))
			renderOverlays();
	}

	@Override
	public EnumSet<TickType> ticks() {
		return EnumSet.of(TickType.RENDER);
	}

	@Override
	public String getLabel() {
		return null;
	}
	
	private void renderOverlays() {
		Minecraft mc = FMLClientHandler.instance().getClient();
		if (mc.renderViewEntity != null && mc.gameSettings.thirdPersonView == 0 && !mc.renderViewEntity.isPlayerSleeping() 
				&& mc.thePlayer.isInsideOfMaterial(MinechemBlocks.materialGas))
        {
			GL11.glDisable(GL11.GL_ALPHA_TEST);
	        int overlayTexture = mc.renderEngine.getTexture("/misc/water.png");
	        GL11.glBindTexture(GL11.GL_TEXTURE_2D, overlayTexture);
	        renderWarpedTextureOverlay(0, mc);
			GL11.glEnable(GL11.GL_ALPHA_TEST);
        }
	}
	
	/**
     * Renders a texture that warps around based on the direction the player is looking. Texture needs to be bound
     * before being called. Used for the water overlay. Args: parialTickTime
     */
    private void renderWarpedTextureOverlay(float par1, Minecraft mc)
    {
        Tessellator var2 = Tessellator.instance;
        float var3 = mc.thePlayer.getBrightness(par1);
        GL11.glColor4f(var3, var3, var3, 0.5F);
        GL11.glEnable(GL11.GL_BLEND);
        GL11.glBlendFunc(GL11.GL_SRC_ALPHA, GL11.GL_ONE_MINUS_SRC_ALPHA);
        GL11.glPushMatrix();
        float var4 = 4.0F;
        float var5 = -1.0F;
        float var6 = 1.0F;
        float var7 = -1.0F;
        float var8 = 1.0F;
        float var9 = -0.5F;
        float var10 = -mc.thePlayer.rotationYaw / 64.0F;
        float var11 = mc.thePlayer.rotationPitch / 64.0F;
        var2.startDrawingQuads();
        var2.addVertexWithUV((double)var5, (double)var7, (double)var9, (double)(var4 + var10), (double)(var4 + var11));
        var2.addVertexWithUV((double)var6, (double)var7, (double)var9, (double)(0.0F + var10), (double)(var4 + var11));
        var2.addVertexWithUV((double)var6, (double)var8, (double)var9, (double)(0.0F + var10), (double)(0.0F + var11));
        var2.addVertexWithUV((double)var5, (double)var8, (double)var9, (double)(var4 + var10), (double)(0.0F + var11));
        var2.draw();
        GL11.glPopMatrix();
        GL11.glColor4f(1.0F, 1.0F, 1.0F, 1.0F);
        GL11.glDisable(GL11.GL_BLEND);
    }

}