Wizardry/src/main/java/electroblob/wizardry/client/renderer/RenderArc.java

package electroblob.wizardry.client.renderer;

import org.lwjgl.opengl.GL11;

import electroblob.wizardry.Wizardry;
import electroblob.wizardry.entity.EntityArc;
import net.minecraft.client.renderer.GlStateManager;
import net.minecraft.client.renderer.OpenGlHelper;
import net.minecraft.client.renderer.Tessellator;
import net.minecraft.client.renderer.VertexBuffer;
import net.minecraft.client.renderer.entity.Render;
import net.minecraft.client.renderer.entity.RenderManager;
import net.minecraft.client.renderer.vertex.DefaultVertexFormats;
import net.minecraft.util.ResourceLocation;

public class RenderArc extends Render<EntityArc> {

	private static final ResourceLocation[] textures = new ResourceLocation[16];

	public RenderArc(RenderManager renderManager){
		super(renderManager);
		for(int i = 0; i < 16; i++){
			textures[i] = new ResourceLocation(Wizardry.MODID, "textures/entity/arc_" + i + ".png");
		}
	}

	@Override
	public void doRender(EntityArc arc, double d0, double d1, double d2, float fa, float fb){
		GlStateManager.pushMatrix();
		GlStateManager.translate((float)d0, (float)d1, (float)d2);
		GlStateManager.disableLighting();
		GlStateManager.enableBlend();
		GlStateManager.blendFunc(GL11.GL_SRC_ALPHA, GL11.GL_ONE_MINUS_SRC_ALPHA); // This line fixes the weird
																					// brightness bug.
		OpenGlHelper.setLightmapTextureCoords(OpenGlHelper.lightmapTexUnit, 240f, 240f);

		// System.out.println("Entity coords: " + entity.posX + ", " + entity.posY + ", " + entity.posZ);
		// System.out.println("doRender parameters: " + d0 + ", " + d1 + ", " + d2 + ", " + fa + ", " + fb);

		Tessellator tessellator = Tessellator.getInstance();
		VertexBuffer buffer = tessellator.getBuffer();

		bindTexture(textures[arc.textureIndex]); // This MUST be after the tessellator declaration and the gl stuff

		/**
		 * Note: A lot of the maths here works on similar triangles and the ratios between them, avoiding too much
		 * pythagoras and eliminating the need for any trig. Ratios are used for the positioning of the arc endpoints.
		 * Ratios are usually used swapping x and z because the triangles are rotated through 90 degrees.
		 */

		double dx = -d0;
		double dy = -d1;
		double dz = -d2;

		if(arc.x1 != 0){
			dx = arc.x1 - arc.posX;// - d2/lengthOffsetRatio;
			dy = arc.y1 - arc.posY + 0.3;
			dz = arc.z1 - arc.posZ;// + d0/lengthOffsetRatio;

			// The distance from caster to target
			double arcLength = Math.sqrt(dz * dz + dx * dx);

			// The ratio between the length of the arc and the offset of the start point from the player's centre (which
			// is always 0.3).
			// double lengthOffsetRatio = arcLength/0.3;

			// EntityClientPlayerMP player = Minecraft.getMinecraft().player;

			// double xViewDist = player.posX - d0;
			// double yViewDist = player.posY + player.eyeHeight - d1;
			// double zViewDist = player.posZ - d2;

			// double xzViewDist = Math.sqrt(xViewDist * xViewDist + zViewDist * zViewDist);

			// The angle above the horizontal that this particular player is viewing the arc from
			// double viewAngle = Math.atan(yViewDist/xzViewDist);

			// Half the width of the arc
			double arcWidth = 0.3d;

			// Right hand side of vertical plane
			buffer.begin(GL11.GL_QUADS, DefaultVertexFormats.POSITION_TEX);
			// Target end
			buffer.pos(0, -0.5, 0).tex(1, 1).endVertex();
			buffer.pos(0, 0.5, 0).tex(1, 0).endVertex();
			// Caster end
			buffer.pos(dx, dy, dz).tex(0, 0).endVertex();
			buffer.pos(dx, dy - 1, dz).tex(0, 1).endVertex();
			tessellator.draw();

			// Left
			buffer.begin(GL11.GL_QUADS, net.minecraft.client.renderer.vertex.DefaultVertexFormats.POSITION_TEX);
			// Target end
			buffer.pos(0, -0.5, 0).tex(1, 1).endVertex();
			// Caster end
			buffer.pos(dx, dy - 1, dz).tex(0, 1).endVertex();
			buffer.pos(dx, dy, dz).tex(0, 0).endVertex();
			// Target end
			buffer.pos(0, 0.5, 0).tex(1, 0).endVertex();
			tessellator.draw();

			// Bottom of horizontal plane
			buffer.begin(GL11.GL_QUADS, net.minecraft.client.renderer.vertex.DefaultVertexFormats.POSITION_TEX);
			buffer.pos((arcWidth / arcLength) * dz, 0, (-arcWidth / arcLength) * dx).tex(1, 1).endVertex();
			buffer.pos(dx + (arcWidth / arcLength) * dz, dy - 0.5, dz - (arcWidth / arcLength) * dx).tex(0, 1)
					.endVertex();
			buffer.pos(dx - (arcWidth / arcLength) * dz, dy - 0.5, dz + (arcWidth / arcLength) * dx).tex(0, 0)
					.endVertex();
			buffer.pos((-arcWidth / arcLength) * dz, 0, (arcWidth / arcLength) * dx).tex(1, 0).endVertex();
			tessellator.draw();

			// Top
			buffer.begin(GL11.GL_QUADS, net.minecraft.client.renderer.vertex.DefaultVertexFormats.POSITION_TEX);
			buffer.pos((arcWidth / arcLength) * dz, 0, (-arcWidth / arcLength) * dx).tex(1, 1).endVertex();
			buffer.pos((-arcWidth / arcLength) * dz, 0, (arcWidth / arcLength) * dx).tex(1, 0).endVertex();
			buffer.pos(dx - (arcWidth / arcLength) * dz, dy - 0.5, dz + (arcWidth / arcLength) * dx).tex(0, 0)
					.endVertex();
			buffer.pos(dx + (arcWidth / arcLength) * dz, dy - 0.5, dz - (arcWidth / arcLength) * dx).tex(0, 1)
					.endVertex();
			tessellator.draw();
		}

		GlStateManager.enableLighting();
		GlStateManager.disableBlend();
		GlStateManager.popMatrix();
	}

	@Override
	protected ResourceLocation getEntityTexture(EntityArc entity){
		return textures[entity.textureIndex];
	}

}