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learn-wgpu/assets/js/30.f08bd92d.js

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QTIgAAQDohAgAApBMiAABAOiECAACkEyIAAEA6IQIAAKQTIgAAQDohAgAApBMiAABAOiECAACkEyIAAEA6IQIAAKQbjoh4ZH1r0OsAAAAa5P8D75CpLfCP/NcAAAAASUVORK5CYII="},435:function(t,s,a){"use strict";a.r(s);var n=a(7),e=Object(n.a)({},(function(){var t=this,s=t._self._c;return s("ContentSlotsDistributor",{attrs:{"slot-key":t.$parent.slotKey}},[s("h1",{attrs:{id:"buffers-and-indices"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#buffers-and-indices"}},[t._v("#")]),t._v(" Buffers and Indices")]),t._v(" "),s("h2",{attrs:{id:"we-re-finally-talking-about-them"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#we-re-finally-talking-about-them"}},[t._v("#")]),t._v(" We're finally talking about them!")]),t._v(" "),s("p",[t._v("You were probably getting sick of me saying stuff like \"we'll get to that when we talk about buffers\". Well now's the time to finally talk about buffers, but first...")]),t._v(" "),s("h2",{attrs:{id:"what-is-a-buffer"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#what-is-a-buffer"}},[t._v("#")]),t._v(" What is a buffer?")]),t._v(" "),s("p",[t._v("A buffer is a blob of data on the GPU. A buffer is guaranteed to be contiguous, meaning that all the data is stored sequentially in memory. Buffers are generally used to store simple things like structs or arrays, but they can store more complex stuff such as graph structures like trees (provided all the nodes are stored together and don't reference anything outside of the buffer). We are going to use buffers a lot, so let's get started with two of the most important ones: the vertex buffer, and the index buffer.")]),t._v(" "),s("h2",{attrs:{id:"the-vertex-buffer"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#the-vertex-buffer"}},[t._v("#")]),t._v(" The vertex buffer")]),t._v(" "),s("p",[t._v("Previously we've stored vertex data directly in the vertex shader. While that worked fine to get our bootstraps on, it simply won't do for the long term. The types of objects we need to draw will vary in size, and recompiling the shader whenever we need to update the model would massively slow down our program. Instead, we are going to use buffers to store the vertex data we want to draw. Before we do that though we need to describe what a vertex looks like. 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2.")]),t._v("\n")])])]),s("p",[t._v("A couple things to note:")]),t._v(" "),s("ol",[s("li",[t._v("The method name is "),s("code",[t._v("set_index_buffer")]),t._v(" not "),s("code",[t._v("set_index_buffers")]),t._v(". You can only have one index buffer set at a time.")]),t._v(" "),s("li",[t._v("When using an index buffer, you need to use "),s("code",[t._v("draw_indexed")]),t._v(". The "),s("code",[t._v("draw")]),t._v(" method ignores the index buffer. Also make sure you use the number of indices ("),s("code",[t._v("num_indices")]),t._v("), not vertices as your model will either draw wrong, or the method will "),s("code",[t._v("panic")]),t._v(" because there are not enough indices.")])]),t._v(" "),s("p",[t._v("With all that you should have a garishly magenta pentagon in your window.")]),t._v(" "),s("p",[s("img",{attrs:{src:a(335),alt:"Magenta pentagon in window"}})]),t._v(" "),s("h2",{attrs:{id:"color-correction"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#color-correction"}},[t._v("#")]),t._v(" Color Correction")]),t._v(" "),s("p",[t._v("If you use a color picker on the magenta pentagon, you'll get a hex value of #BC00BC. If you convert this to RGB values you'll get (188, 0, 188). Dividing these values by 255 to get them into the [0, 1] range we get roughly (0.737254902, 0, 0.737254902). This is not the same as what we are using for our vertex colors, which is (0.5, 0.0, 0.5). The reason for this has to do with color spaces.")]),t._v(" "),s("p",[t._v("Most monitors use a color space known as sRGB. Our surface is (most likely depending on what is returned from "),s("code",[t._v("surface.get_preferred_format()")]),t._v(") using an sRGB texture format. The sRGB format stores colors according to their relative brightness instead of their actual brightness. The reason for this is that our eyes don't perceive light linearly. We notice more differences in darker colors than we do in lighter colors.")]),t._v(" "),s("p",[t._v("You get the correct color using the following formula: "),s("code",[t._v("srgb_color = ((rgb_color / 255 + 0.055) / 1.055) ^ 2.4")]),t._v(". Doing this with an RGB value of (188, 0, 188) will give us (0.5028864580325687, 0.0, 0.5028864580325687). A little off from our (0.5, 0.0, 0.5). Instead of doing manual color conversion, you'll likely save a lot of time by using textures instead as they are stored as sRGB by default, so they don't suffer from the same color inaccuracies that vertex colors do. We'll cover textures in the next lesson.")]),t._v(" "),s("h2",{attrs:{id:"challenge"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#challenge"}},[t._v("#")]),t._v(" Challenge")]),t._v(" "),s("p",[t._v("Create a more complex shape than the one we made (aka. more than three triangles) using a vertex buffer and an index buffer. Toggle between the two with the space key.")]),t._v(" "),s("WasmExample",{attrs:{example:"tutorial4_buffer"}}),t._v(" "),s("AutoGithubLink")],1)}),[],!1,null,null,null);s.default=e.exports}}]);
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