after drawing each light and shadow pair, we bring the _z value closer to the screen so the next light will be over the previous shadows. The lights previously drawn that are under the shadow will not be affected since the shadow is transparent. The cool thing is, even if the shadow is transparent, the light will not be able to draw over the shadow. This lets the shadow be drawn over the light, even if the shadow is drawn first. the only difference is that the shadow sets its z coordinate to u_z -0.5, while the light sets its shadow to just u_z. Remember the u_z variable in the light shader? it is also present in the shadow shader. Gpu_set_zwriteenable(0) we turn on ztestenable and zwriteenable to allow the use of Z-buffer depth handling. _z- //Next set of shadows and lights is set closer to the screen But in order to do this, we will need to utilize the Z-buffer to handle the depth.īefore we go to the draw function, let us first setup the shader uniform variables in the setup obejct create:ĭraw_rectangle(0,0,320,180,0) //canvas for drawing the light Note that we are drawing an invisible shadow (fragment shader code) but don't worry, this shadow will be used to block its corresponding light without affecting the previous lights, that's how we can draw all the lights directly without needing to draw on a separate surface. this common vertex buffer will be reconfigured differently through the shaders by changing the light position passed through the shader. I will need to only create one common shadow vertex buffer for all lights instead of creating unique vertex buffers for every light. The big difference with my method compared to Mike Daily's is mine is calculated in the GPU. We add this length to the wall end points and we get the end points of the shadow. Multiply it with a large number and you get a vector with the same slope as the distance but with a very long length. We get the vector distance from the light source to the end of the wall then divide it by the the scalar distance to get the unit vector. This is very similar to how Mike Daily positioned his vertices. }What this shader does is, if the vertex that was passed through the shader contains a z coordinate that is greater than zero, it will reposition the vertex x and y position based on the light position, u_pos. Gl_FragColor = vec4(0.) //draws an invisible shadow that can block the light when Z-buffer is on This is done in the object setup step function. It's a simple optimization that works and reduces the amount of quads constructed by half. With each wall, we will draw the quads using the diagonals of the block. Those with z position at 1 will be later repositioned in the shader so the quad will be drawn. If you forget the z coordinate, this will create a single line. If you inspect the code carefully, you will notice that the vertices will either have both x1 and y1 or both x2 and y2, never a mixture of x1 and y2 or x2 and y1. x1 y1 represents one end of the wall and x2 y2 represents the other end of the wall. Vertex_position_3d(_vb,_x2,_y2,1) //repositioned vertex Vertex_position_3d(_vb,_x1,_y1,1) //repositioned vertex Z coordinate is used as a flag to determine if the vertex will be repositioned in the shader G3d_light_get_output_level(Object, RedGreenOrBlue) Returns the Red, Green or Blue Light Output colour component assigned to the specified instance.//Creates Quad with two triangles. This function is very useful for colour correcting the highlights. G3d_light_set_output_level(Object, Red, Green, Blue) Sets the Light Output Level for the specified instance. RedGreenOrBlue argument can be one of the following values: RedGreenOrBlue: colour component to return. G3d_light_get_input_level(Object, RedGreenOrBlue) Returns the Red, Green or Blue Light Input colour component assigned to the specified instance. Green: Green component value from 0 to 1. Object: A valid GameMaker: Studio Object ID. This function is very useful for colour correcting the shadows. G3d_light_set_input_level(Object, Red, Green, Blue) Sets the Light Input Level for the specified instance. Once initialized a GameMaker: Studio Object with g3d_object_init() function, thanks to Giavapps 3D Lighting Engine you have also access to the following functions: This feature does not work correctly for Shaders.ĭ3d_light_define_direction(Index, X, Y, Z, Colour) Supported.ĭ3d_light_define_point(Index, X, Y, Z, Range, Colour) Supported.ĭ3d_light_enable(Index, Enable) Supported.ĭ3d_light_define_ambient(Colour) Supported.
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