entity_renderer.java

@Override
    public void render(HoldoutEntity holdout, float yaw, float partialTick, PoseStack ps, MultiBufferSource multiBufferSource, int packedLight) {
        Vec3 pos = holdout.position();
        RenderSystem.enableDepthTest();
        LaggingMaskRenderTarget.draw(holdout.level().getGameTime());

        if (!(multiBufferSource instanceof MultiBufferSource.BufferSource buffer)) return;
        RenderSystem.enableDepthTest();
        LaggingMaskRenderTarget.use(() -> {
//            Renderer3d.renderFilled(ps, Color.WHITE, new Vec3(0, 70, 0), new Vec3(2, 2, 2));


            int colour = 0xffffffff;
            int black = 0;



            float inner = 1f;
    //        float hitboxSize = 4f / 16f;

            Vector3f innerSize = new Vector3f(inner, inner, inner);

            ps.pushPose();

            ps.mulPose(Axis.YP.rotationDegrees(180f - yaw));
    //        ps.mulPose(Axis.XP.rotationDegrees(180 - nix.getXRot()));
            ps.mulPose(Axis.ZP.rotationDegrees(180f));

            int light = LevelRenderer.getLightColor(holdout.level(), BlockPos.containing(holdout.position()));
            RenderSystem.enableDepthTest();
            drawCube(holdout, innerSize, new Vector3f(-innerSize.x / 2f, -innerSize.y / 2f, innerSize.z / 2f), ps, buffer, 16, 0x00_ffffff);
            RenderSystem.enableDepthTest();
            ps.popPose();

        });
        RenderSystem.enableDepthTest();
        super.render(holdout, yaw, partialTick, ps, multiBufferSource, packedLight);
        RenderSystem.enableDepthTest();
    }

render_target.java

package dev.kineticcat.complexhex.client.render.entity.holdoutrenderingshenannigans;//package dev.kineticcat.complexhex.client.render.entity.holdoutrenderingshenannigans;//package dev.kineticcat.complexhex.client.render.entity.holdoutrenderingshenannigans;

import com.mojang.blaze3d.pipeline.RenderTarget;
import com.mojang.blaze3d.platform.GlStateManager;
import com.mojang.blaze3d.systems.RenderSystem;
import dev.kineticcat.complexhex.ComplexhexClient;
import net.minecraft.client.Minecraft;
import org.lwjgl.opengl.GL30C;

// this whole thing and associated files only exist due to the help of "0x150" on the fabric dc server lmao
public class LaggingMaskRenderTarget extends RenderTarget {
    private static LaggingMaskRenderTarget instance;

    private LaggingMaskRenderTarget(int width, int height) {
        super(false);
        RenderSystem.assertOnRenderThreadOrInit();
        this.resize(width, height, true);
        this.setClearColor(0f, 0f, 0f, 0f);
    }

    private static LaggingMaskRenderTarget obtain() {
        if (instance == null) {
            instance = new LaggingMaskRenderTarget(
                    Minecraft.getInstance().getMainRenderTarget().width,
                    Minecraft.getInstance().getMainRenderTarget().height);
        }
        return instance;
    }

    public static void use(Runnable r) {
        RenderTarget mainBuffer = Minecraft.getInstance().getMainRenderTarget();
        RenderSystem.assertOnRenderThreadOrInit();
        LaggingMaskRenderTarget buffer = obtain();
        if (buffer.width != mainBuffer.width || buffer.height != mainBuffer.height) {
            buffer.resize(mainBuffer.width, mainBuffer.height, false);
        }
        GlStateManager._glBindFramebuffer(GL30C.GL_DRAW_FRAMEBUFFER, buffer.frameBufferId);
        buffer.bindWrite(true);
        r.run();
        buffer.unbindWrite();

        GlStateManager._glBindFramebuffer(GL30C.GL_DRAW_FRAMEBUFFER, mainBuffer.frameBufferId);
        mainBuffer.bindWrite(false);
    }

    public static void draw(long time) {
        RenderTarget mainBuffer = Minecraft.getInstance().getMainRenderTarget();
        LaggingMaskRenderTarget buffer = obtain();
        ComplexhexClient.mse.setSamplerUniform("Mask", buffer);
        ComplexhexClient.mse.setUniformValue("time", (float) time);
        ComplexhexClient.mse.render(Minecraft.getInstance().getDeltaFrameTime());
        buffer.clear(false);
        mainBuffer.bindWrite(false);
    }
}